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By Rolland L. Blake

Petrographic and mineralogical studies were made on unoxidized samples from the Cuyuna and Mesabi districts to study occurrence and properties of the iron phyllosilicate minerals . Examination of 96 thin sections from the thinbedded facies of the main iron - formation of the Cuyuna district indicates that the most abundant minerals are Mn - Mg - siderite , stilpnome lane , and minnesotaite . Reconstitution and recrystallization of minerals has occurred along certain beds , and textures indicate that some minnesotaite apparently formed at expense of stilpnomelane . Three samples of stilpnome lane and one of minnesotaite were concentrated from fracture - fillings within iron- formation . Results of chemical , optical , spectrographic , X- ray diffraction , and differential thermal analyses on these samples are reported . The detection of ammonia in stilpnome lane samples is the first such occurrence reported , and its significance is discussed . New mineral data are presented on greenalite and probable septechamosite from the Mesabi district .

Jan 1, 1964

By G. A. Christie

This paper presents a vision system capable of providing an accurate estimate for the volume of stockpiles using 2D images. By imaging a stockpile from multiple viewpoints with a two-camera system, a 3D point cloud of known scale is generated using image-based 3D reconstructions. With a small amount of user interaction, the points that correspond to the surface of the stockpile are extracted and used to measure the volume. The hardware required for the two-camera system is light enough to be carried by a small unmanned aircraft and is a cheaper alternative to LiDAR while still being competitive in terms of accuracy. When testing the volume measurement algorithm on a stockpile of known volume, the measured output was found to have less than a 3% error from the ground truth.

By H. M. St. John

Like every present-day manufacturer, the brass foundryman is faced with the necessity of reducing the cost of his finished product without impairing its appearance or quality. He must use every economy that the progress of art and science puts at his disposal and should also be alert to profit by any peculiarity in his own situation or the nature of his product that may give him an exceptional advantage. Much can be accomplished by the adoption of labor-saving equipment and improved methods of melting, molding and handling. Control of pouring temperature, study of defective castings and their causes, laboratory control of molding sand and core mixtures, the use of less expensive alloys, all contribute to the desired end. Assuming that the composition of the alloy is already as inexpensive as the character of the casting will permit, still further savings can be made by the intelligent purchase and utilization of the metals needed to produce the desired analysis. Functions of Secondary and Virgin Metals in Casting Brass It is no longer a general assumption among foundrymen that quality castings must be made from an "all virgin" mix. If suitable secondary metals can be obtained more cheaply it is wasteful to use any larger proportion of virgin metal than is required to produce castings of the desired properties. To follow such a course, however, imposes upon the foundryman a heavier obligation than was formerly the case, to make sure by test and inspection that his castings really are of the desired quality. So long as he used the most expensive grades of metal and his melting practice was reasonably correct he was not obliged to give much thought to the quality of the metal in the castings. If he is to use secondary metals he must, in order to retain the confidence of his customer, examine these metals very carefully before use, exercise scrupulous control over his melting and pouring conditions and examine his castings closely. These statements apply more particularly to the jobbing foundry. The foundry department in a manufacturing plant is in a somewhat

Jan 1, 1930

By Douglass D. Donald

The New Jersey Zinc Co. successfully holed through a 2 ½ -mile haulage tunnel connecting its new Ivanhoe shaft with the Van Mater Shaft at Austinville, Va. This 8 x 10-ft cross-section tunnel was driven from both ends and met at a point approximately a mile from one shaft and a mile and a half from the other. In order to make certain that the faces met accurately on line and grade it was necessary to refine conventional mine surveying practices. The mines that are serviced by these shafts are located in the southwestern part of Virginia approximately midway between Roanoke and Bristol at the west foot of the Blue Ridge. While the presence of lead-zinc sulfide ores has been known in this area for more than 200 years, it was in 1902 that New Jersey Zinc Co. acquired the Austinville property, which has been in constant operation since that time. About ten years ago the company undertook an extensive diamond drilling program at Ivanhoe several miles to the southwest. This program was successful in locating sufficient ore to justify the purchase of a number of the properties in this area and plans were made to develop the new orebodies. The discovery of this ore as well as substantial additional reserves at Austinville resulted in a decision by the company to increase its daily milling capacity to 3000 tons, of which about 1000 tons would be supplied from the Ivanhoe mine.

Jan 9, 1958

By Cláudio Magno do Carmo, Gilmar Pinto Ribeiro, Luciney Miranda Martins

A rotina operacional e os seus processos de validação e acompanhamento já estão consolidados no ambiente da Tecnologia da Informação (TI). No ambiente da Tecnologia de Automação (TA) estamos avançando lentamente, apesar da grande semelhança em vários processos, devido a dificuldades de adaptação dos controles principalmente no tocante aos tempos de resposta e atuação das equipes. Enquanto a TI atua na garantia da execução do tripé formado por confidencialidade (segurança), integridade (precisão dos dados) e disponibilidade, rigorosamente nessa sequência de prioridades (CID) [1], a TA procura atender às necessidades da produção, e inverte a prioridade para a disponibilidade (DIC). Daí o conflito inicial entre os modelos: demanda imediata ou planejamento detalhado das atividades dentro dos padrões de qualidade da TI, entretanto sem impactar nas metas operacionais. É tudo uma questão de visão e principalmente de gestão por processos! Quais as diretrizes comuns? Quais os processos similares? Encontrar os pontos de afinidade, alinhados com as expectativas dos gestores e com foco na disponibilidade, sem perder a integridade e confiabilidade dos dados é o desafio.

Oct 1, 2019

By M. E. Mellado

In this paper, we present an a posteriori validation of a heap leaching analytical model using sensitivity analysis. The model is suitable to represent the process of heap leaching of solid reactants from porous pellets and is based on a combination of the leaching kinetics at two levels: particle and heap. The validation is simple, and a sensitivity analysis can easily be performed. The simplicity of the analysis provides insight into the control and optimization of the heap leaching process without strong mathematical complexities. The model and the corresponding sensitivity analysis include the effects of heap height, particle sizes, flow rates and several operation-design variables. Using a case study, we discuss the importance of model validation based on sensitivity analysis. We also comment on several choices for optimizing the process. We had three goals in this work: a posteriori validation, highlighting the importance of model validation and providing insight into optimization choices. We can conclude that the model has good internal logic and there are no extra variables; i.e., all of the variables in the model are necessary.

May 1, 2012

The income of the Institute is derived from dues, subscriptions to MINING AND METALLURGY and sale of publications. These sources are fortunately supplemented by the interest from invested funds now amounting to over $500,000, a considerable portion constituting endowments for especial purposes. Aside from the medal funds the principal endowments are the James Douglas Fund for support of the Library, the Rocky Mountain Fund and the Seeley W. Mudd Memorial Fund. The income from the two last named is available for the support of research and a variety of other purposes. It is allocated by the Board of Directors upon recommendation of standing committees in each case. An active effort is being made to increase the endowments of the Institute, it being felt that unusual opportunities exist for research and public and professional service through the organization and at a minimum of expense. J. V. W. Reynders is chairman of the Endowment Committee.

Jan 1, 1923

By R. A. Brackett

The most effective means of controlling the dust in the drilling of rock has been found after careful investigation to be collection of this dust at the source. By direct collection, all the dust is collected at the collar of the drill hole and deposited into suitable containers. Equipment for handling this work can be either portable or stationary, depending upon the particular requirements and the application. For most work the portable unit is found most advantageous, and with a capacity capable of handling two drills operating simultaneously. Such a portable unit would consist of a metal cap, or hood, placed against the face of the rock through which the drill steel would be inserted. This hood is connected by a flexible rubber hose to a primary separator, where the bulk of the dust is collected. From here a second length of hose connects to the secondary stage of separation, where the fine particles of dust are collected and which is built in as an integral part of the vacuum producer. Hoods are adapted for vertical, horizontal or stope drilling, and mounted so as to become immediately effective when collaring the hole and remain in place continuously. Such dust collectors can be used with either wet or dry drilling. However, in view of the fact that when drilling dry and using the dust collector, the dust count can be maintained within safe limits, wet drilling becomes unnecessary. Furthermore, it has been found that when using the dust collector not only has the dust hazard been eliminated, but also increased footage can be obtained. Samples taken under a wide variation of conditions indicate that where the dust count required is below five million particles per cubic foot, dust collectors will be required. Opreators, in general, accept the use of this additional equipment favorably, and it is generally felt that such means of collecting the dust will soon be universally adopted. Tests made by the Connecticut Department of Health Bureau of Occupational Diseases show dust counts reduced from 203 million particles to 6.05 million by the use of the dust collector, when drilling dry.

Jan 1, 1934

By G. R. Love, M. L. Picklesimer

Aboue 950°C the Nb-Zr system consists of a completely miscible bcc solid solution, commonly called the phase. Between 950 and 600°C, and between 20 and 85 pct Nb, the phase deconlposes, after sunciently long times, into two bcc solid solutions. The pct Zr alloys are conveniently descibecl with T-T-T (time-temperature-transformation) curves having a nose at about 2 hr at 700°C. The reaction rate varies only slowly with zirconium content and negligibly with oxygen contanzination; it is speeded up by a factor of 10 to 15 by 90 pct cold ulork and slowed dou by n factor oj 10 to 30 by a two-hundrecljold increase in grain size. Nb-r alloys with compositions between 40 and 85 pct Nb have been the basis for the majority of commercially important superconducting materials. In part because of their commercial promise, more is known about these alloys than about most other high-field superconducting materials. At the same time, there is considerable disputed or incomplete metallurgical information. For example, although Rogers and tkins&apos; indicate a monotectoid reaction at approximately 600°C and a two-phase 01 + 0, field extending between 20 and 85 pct Nb and to a maximum of 95OGC, erhout&apos; has reported that this entire region would be a single homogeneous B were it not for oxygen contamination. Again, although it has been shown that relatively short-time heat treatments in the vicinity of 700CZ significantly improve the ability of short wire samples to carry high currents in high magnetic fields at 4.2K, these observations have never been fully correlated with the structural change or changes occurring during the anneal. We intend to investigate in detail the effect of metallurgical variables, including heat treatment, on the superconducting properties of hard superconductors. To verify that our experimental techniques are valid and to establish a relative standard against which other materials may be measured, we feel it advisable to know the behavior of the Nb-Zr alloys under a variety of processing conditions. As an initial step toward this goal, we have determined in detail the kinetics of the transformations in Nb-Zr alloys. EXPERIMENT A number of problems had to be solved before beginning any fruitful work on the reaction kinetics in this system. While solving some of these problems, either by chance or by design, small amounts of information were obtained about alloys containing 40, 50, 60, 65, 67, 70, and 75 pct Nb, bal. Zr. In addition, a large range of grain sizes and a range of temperatures considerably greater than the range indicated by Rogers and Atkins phase diagram were examined. We will, however, report in detail only the results obtained for the Nb + 33 pct Zr and Nb + 25 pct Zr alloys at three grain sizes, two levels of oxygen contamination, and the temperature range 550 to 950°C. These data are most complete, but the other data are sufficiently complete to indicate the kind and magnitude of the variation of the transformation kinetics outside this range. The first and most difficult problem encountered in this inquiry was one of sample homogeneity. When Nb-Zr alloys are arc- or electron-beam-melted on a cooled copper hearth, solidification is sufficiently slow that there is appreciable coring in the cast structure and a large variation of grain size across the button thickness. Both these factors significantly affect the apparent reaction rate in the system. A two-step solution to the problem was attempted; an arc-melting and drop-casting technique has been developed by conald that greatly reduces the as-cast grain size and virtually eliminates coring segregation. Ingots made in this way exhibited no detectable (3 pct maximum) zirconium segregation. Before it was evident just how good this technique was, we attempted to supplement it with rather long-time, high-temperature annealing of the cast ingots. This annealing was carried out in evacuated and sealed (seal-off pressures < 1.0 x 106 torr) quartz capsules lined with tantalum foil at 1400 to 1450 C for 8 to 72 hr. There were two principal effects of this treatment: the grain size increased to a fairly uniform 150 p, and the surface and all grain boundaries near the surface acquired a film of a second phase, tentatively identified as an oxide (possibly additionally contaminated with silicon). There was no evidence that this 1400 C treatment had affected the zirconium segregation. High-temperature annealing was subsequently used only for grain-size control, but anneals of longer than 4 hr at temperatures greater than 1000°C were performed in dynamic vacuums (pressure no greater than 1.0 x lo torr). Any contamination resulting from these treatments was well below the limits of detection of our techniques. All samples, as cast, were cold-swaged to at least 85 pct reduction in area. The samples called cold-worked were tested as swaged. The minimum re-crystallization anneal for these alloys was about 12 hr at 1050 C; this produced an equiaxed grain diameter of about 4 to 8 P. Annealing for 4 hr at 1450°C produced a grain size of about 80 to 150 p; and annealing for 4 hr at 1650aC, close to the melting point of many of these alloys, produced a grain size of 0.5 to 1.0 mm. At all temperatures, the larger grain size was

Jan 1, 1967

By M S. Sandhu

Singrauli area of Madhya Pradesh in India has been developed as the power capital expected to produce around 11000 MW in near future requiring 65 million tonnes of Coal per annum. Thermal power plants were installed considering the vicinity of coal reserves which are minable by open cast mining methods. Crisis of oil in seventies further expedited the process of planning big open-cast projects in the area varying from capacity of 3 million tonnes of coal to 14 million tonnes per annum. A separate company - Northern Coalfields Ltd. was formed to ensure meeting the rising demand of coal required for energy production. Northern Coalfields at present is producing 35 million tonnes of coal and will reach the capacity of peak demand of 65 million tonnes by the turn of the century.

Jan 1, 1998

By M. J. Richards

Spontaneous combustion caused by the movement of air through the waste is a major problem. Combat methods attempt to exclude oxygen rich air, but little is known about airflow through the waste. The use of a tracer gas technique to monitor the flow of nitrogen from an injection hole during inertisation is described. Correlations are drawn between barometric pressure changes and the nitrogen entering the waste. As no information was obtained about airflow and oxidation zones, a second experiment was conducted to sample from the waste, but the results were inconclusive. A finite element method developed to model the pressure and airflow distribution, under steady state and nitrogen injection conditions is outlined

Jan 1, 1987

NORTH AMERICA ALASKA Anchorage,-Ames, M. B. Culver, H. W. Fiedler, H. L. Fox, E. F. Gallemore, W. A. Kreitlow, E. J. Layfield, R. A. Saarela, L. H. Strandberg. H. Candle,-Bobbins, J. S. College.-Fackler, W. C. Joesting, H. R. Swift. R. E. "Wilcox, H. G.. Crooked Creek-Lyman. R. F. Fairbanks.-Beistline, E. H. CANADA Canadian Army Overseas,¬ Ball, H. D. Brides, C. Butterill. H. J. M. Ladner, F. E. Lane, H. C. Millar, R&apos;. A. Murchison, R. G. Passow, F. M. ALBERTA Calgary-Allen, R. E. de Hart. J. B. Dingman, C. W. Furnical. G. H. Gray, J. G.

Jan 1, 1943

By L. B. Berger, W. P. Yant, J. B. Littlefield

"INTRODUCTION Hydrogen sulphide (H2S) is one of the most toxic industrial gases and of relatively wide occurrence in industry. Among its common industrial occurrences are, in the production and refining of high-sulphur petroleum, in natural gases, in gypsum and sulphur mining, in rock strata and underground waters (where it is encountered in tunneling and caisson work) in blasting with black powder and in blasting high-sulphide ores with other explosives, in gas manufacture, in the carbonization of coal, and in the manufacture of chemicals.The usual methods of detection, other than by the sense of smell, which is lost in 2 to 15 minutes' exposure to 0.010. to 0.015 percent of this gas, 5/ either are too cumbersome for frequent and rapid analyses or, like the wet lead acetate paper test, afford only qualitative results. A qaantitative determination usually involves the use of solutions, bubblers, flowmeters, standard solutions, burettes, and indicators manipulated by trained technical men. All apparatus and methods in common laboratory use are, in general, unsuitable for the field.The physiological response attending exposure to various Concentrations of hydrogen sulphide in air, is as follows, in percent by volume 6/:0.005 to 0.010: Subacute poisoning - slight symptoms, such as mild conjunctivitis and respiratory-tract irritation after 1-hour exposure."

Jun 1, 1935

By Stafford McKnight, Larissa Koroznikova, Steve Hall, Cameron Klutke

This paper outlines a simple methodology for mineral characterisation, developed as part of the Australian Mineral Industry Research Association (AMIRA) managed research project P777 ?The Development of Heavy Suspension Techniques for High Density Separations (Replacement of Clerici?s Solution)?. The project was sponsored by De Beers, Rio Tinto and Iluka Resources. Heavy mineral characterisation of samples arising from exploration, mining or metallurgical processes is frequently conducted using laboratory heavy liquid analysis. Unfortunately, there are only a limited number of high density (?heavy?) liquids and these tend to be more toxic as their density increases. Low-toxicity inorganic solutions, based on tungsten compounds, have been developed that can be utilised at relative densities (RD) up to 3.0. Beyond this value organic liquids can be used, however this presents significant health and safety hazards. Diiodomethane (methylene iodide) having a relative density of 3.31 is commonly used. Mixtures of thallium formate and thallium malonate were found in the early 1900?s by Clerici to provide liquids having specific gravities between 4.0 and 5.0. For the characterisation of the heavy components of mineral sand deposits (e.g. anatase RD 3.9, rutile RD 4.2, ilmenite RD 4.4 ? 4.7 and zircon RD 4.6 ? 4.8) there is currently no heavy liquid alternative to Clerici?s solution. Clerici?s solution is highly toxic and testing is now conducted by few laboratories worldwide with costs reflecting the chemical costs, infrastructure costs and health and safety regimes (e.g. blood testing of exposed staff). A simple laboratory technique of density fractionation has been developed, employing suspensions of fine tungsten carbide particles in lithium heteropolytungstates solutions, that can replace Clerici?s solution in the evaluation of fine mineral sands samples (e.g. -250 +150 microns). The developing methodology that can achieve low-cost, low toxic separations at relative densities above 4.0 is outlined and the comparison of results with Clerici?s solution presented. In addition, preliminary work on density fractionation of zircon samples is presented. Zircon fractionation relates to their inclusion, radionuclide content and metamictization.

Jan 1, 2007

By Sergey Romanenko, Tatyana Aleksandrova, Karen Arustamian

"Current status of question about grinding stage effect to electrochemistry parameters of operation preparation slurry before intermediate selective flotation was assessed in the present scientific work. Needs of more detail study chemical reactions in the slurry preparation and flotation processes were shown. The ores are polymetallic sulphide type and the one are most difficult for mineral processing. The methodology allows increase information base during floatation tests. Ionometric methods and elements of neural network have been used in the study of mineral processing questions.We have also identified the relationship between the received values of the electrochemical parameters and the technological results in selective flotation. The optimal values of the electrochemistry parameters in operation of the preparation slurry before selective flotation has been found. The main effect of using the proposed methodology is to obtain scientifically based solutions to improve the technology parameters of flotation polymetallic sulfide ores. Challenging issue of selectivity of sulphide-polymetallic ores will be considered using case study of sulphidepolymetallic ores. It was shown that several factors are formed in ore grinding: formation of hydroxyl oxides of iron compounds, copper cation leaching, metal-sulphide and metal-sulphite complexes formation. The chemistry was revealed for current processes in slurry preparation operation before selective flotation. Quantitative assessment of interrelations between electrochemical parameters of slurry and process performance was given with using electrochemical control methods. Neuron network-based model was estimated based on data array and was allowed to establish optimum electrochemical conditions of metal-sulphite complex formation to provide maximum efficiency of selective flotation.INTRODUCTIONPhysical and chemical processes that take place in ore grinding have a significant impact on flotation selectivity and can cause low selectivity of the flotation process. Today this issue is given much attention. In the paper [1] it is pointed out that sulphide oxidation products and slurry components, such as sulphide ions, metallic iron and its oxidation products, have effect on flotation performance. So, metallic iron has impact on metal-sulphite complex formation as a result of oxidation-reduction reactions as follows:"

Jan 1, 2018

By T. T. Chen, W. Petruk

The mineralogy of the feed, concentrates and tailings from the Heath Steele mill in New Brunswick was studied in detail to determine the liberation and recoveries of the major ore minerals, and to characterize the occurrence and distribution of the trace elements. The ore milled during August 1977 contained an average of 4.34 wt % Zn, 1.25 wt % Cu, 1.64 wt % Pb and 90 gr/ton Ag. The main trace elements in the ore are silver, cadmium, indium, cobalt, antimony, bismuth, arsenic, mercury, tin and gold. Silver is carried in solid solution in tetrahedrite-tennantlte, galena, Ag-Sb sulfosalts and Pb-Bi-Sb sulfosalts. Approximately half of the silver is recovered in the lead and copper concentrates and the remainder is lost in the tailings and Zn concentrate. As the major silver-bearing minerals also contain Sb and Bi, recovering silver by ore dressing would involve recovering elements that are troublesome in extraction metallurgy. Cadmium and most of the indium and mercury occur in solid solution in sphalerite and consequently are recovered in the zinc concentrate. Some indium is also recovered in the copper concentrate in a second unidentified indium-bearing mineral. Cobalt and arsenic occur principally in arsenopyrite, cobaltite, a Co-Fe sulfarsenide, pyrite and pyrrhotite, and follow these minerals into the tailings. Recovery of the valuable element cobalt, therefore, would involve recovering the environmentally hazardous element arsenic. Most of the tin and gold report to tailings. The ore was ground to about 80% minus 270 mesh. At this grind, 71 wt % of the sphalerite, 66 wt % of the chalcopyrite and 59 wt % of the galena were liberated. Recoveries of free sphalerite, free chalcopyrite and free galena in the Zn, Cu and Pb concentrates were 85 wt %, 76 wt % and 80 wt %, respectively; recoveries of unliberated sphalerite, unliberated chalcopyrite and unliberated galena in the respective Zn, Cu and Pb concentrates were 48 wt %, 5 wt % and 7 wt %. Some of the unliberated sphalerite and chalcopyrite grains in the tailings are large and would have been liberated at a finer grind.

Jan 1, 1980

By Truan-Sheng Lui, Li-Hui Chen, Hao-Wen Hsueh, Fei-Yi Hung

"Since Ag wires have similar hardness and bonding properties to Au wires, they can be applied in some pads. In the present study, the annealing effect (at 225°C~275°C for 30min) on the tensile mechanical properties of silver wires with f=23µm was investigated. In addition, the micro-structural characteristics and the mechanical properties before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that with annealing temperatures of more than 250°C, the silver wires possessed a fully annealed structure, the tensile strength and the hardness decreased, and the elongation was raised significantly. Under the thermal effect of EFO, the necks of the Ag balls underwent recrystallization and grain growth was induced, and the annealed Ag wires had a shorter zone of HAZ (220µm). The bonding strength and the neck-strength of the Ag wires were more than 7gf and possessed excellent bonding properties.IntroductionThermosonic ball bonding is one of the preferred processes for electronic packaging to connect a semiconductor chip and a lead frame by a thin metal wire. At present, gold wire and copper wire are the preferred interconnect materials to bond with the aluminum metallized wafer pads [1, 2]. Since gold is expensive and the reliability of copper is poorer [3], the study of silver wire has attracted a lot of attention already. In addition, the inherent properties of high ductility and low hardness of silver as well as its workability effectiveness compared to gold, have made it a preferred alternative .[4, 5]"

Jan 1, 2012

By D. DeGagne, E. De Souza, J. F. Archibald

This paper describes the potential use of anew agent material for backfill consolidation, ground waste glass, to be used as partial replacement of Portland cement fractions within backfill. Significant fractions of commercial and residential silica glass production is currently utilized as waste landfill and must be disposed of at high cost and with no foreseeable environ-mental benefit. This paper also demonstrates that waste glass materials could be effectively recycled as backfill additives, and that a significant, large and stable source of additive supply, currently land filled, can be developed. This new application will generate added value for such materials, serve to promote positive environ-mental stewardship and satisfy engineering sup-port requirements in mines.

Jan 1, 1997

By Jorge Lozano N.

La eficacia de la operación de minado a cielo abierto depende de la optimización de los parámetros empleados en las operaciones de perforación, voladura, carguío y transporte. En este sentido, el texto es un estudio analítico y evaluativo de las operaciones de carguío en la mina Cuajone a través de parámetros como el tipo de material que la pala ha de excavar, ángulos de giro de pala y las velocidades de volquetes en función de las distancias y gradientes por recorrer y así determinar la capacidad de las misma en la operación minera.

Oct 14, 1980

By Robert M. Dreyer

Although lateritic ore deposits are relatively flat-lying, surficial ore bodies, the evaluation of lateritic bauxite and nickel deposits is among the most difficult problems confronting an economic geologist. Laterite is a soil formed under tropical conditions resulting in the concentration, within the soil zone, of certain trivalent metals - principally iron and aluminum, but also, locally, nickel and manganese. The soil zone is divided into two parts: (a) the true soil or lateritic zone and (b) the zone of partially altered bed rock or saprolite. Whereas bauxite generally is confined to the lateritic zone, some nickel deposits occur in both the laterite and saprolite zones. The evaluation of bauxite and lateritic nickel deposits thus has both similarities and differences. These ores have been formed by supergene, soil-forming solutions moving downward through zones of widely varying permeability within the weathering rock. Because the permeability varies widely, both vertically and laterally. the extent of weathering may vary greatly within short distances. Because the weathering process varies widely, the degree of metal concentration may also vary widely. It is not at all uncommon for a laterite to change, within a few centimeters, from a virtually valueless rock to a high grade ore. Moreover, the depth of weathering, and hence the depth and form of the ore profile, vary greatly. Obviously, for this type of deposit, a few grab samples or a few drill holes are virtually worthless. The evaluation of such a deposit requires a sophisticated statistical study based on thousands of carefully selected samples. As a rule of thumb, the cost of evaluating a large bauxite or lateritic nickel deposit will be about one cent per ton of ore in the ground. Thus, the cost of evaluating a several hundred million ton deposit may be considerable. The following factors must be considered during the evaluation: Type of Sampling: The best and most reliable samples for the evaluation of lateritic ores are taken along large, vertical channels in hand-dug pits. Where labor costs are high, some form of drilling may be used in place of pitting, but it is always wise to choose a drilling procedure after checking drilling results against a series of pit channel samples. The drilling may not reproduce exactly the results from pit channel samples, but it may be possible to derive a constant correction factor. If the physical character of the laterite varies within the deposit, it may, of course, be necessary to change the type of drilling, the correction factor or both. In some areas, it has been found empirically that augers, chum drills, vacuum drills, rotary drills, or core drills yield satisfactory results. The problem is to find which drilling technique gives results most similar to channel samples through the heterogeneous sequence characterizing the laterite in a given area. In lateritic nickel deposits, the drilling characteristics of the lateritic and saprolitic portions of the deposit are very different. Within the saprolite, the major nickel values are commonly found in weathered zones within less altered boulders - a type of occurrence which makes sampling very difficult.

Jan 1, 1979