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By John G. Parker

Important quantities of gold, silver, platinum-group metals, selenium, tellurium, and arsenic are recovered in the processing of copper concentrates. The objective of this Bureau of Mines study was to determine the occurrence of these elements in copper ores and to trace their distribution during subsequent processing steps. The study describes the important areas supplying concentrates, precipitates, and unrefined copper to the copper smelting and refining industry in a composite of the years 1971-74. The relative importance of these areas as a source of the respective byproducts is assessed. The lack of certain quantitative and assay data, recycling of dusts and slags, and the addition of scrap to the feed often complicates calculations and estimations of the byproducts in the smelter-refinery throughputs. Such volatile or low-boiling point elements as arsenic, selenium, and tellurium may be lost in gaseous and other emissions in various processing stages, or they may be concentrated in slags and residues for which samples were not available. The effects of antipollution legislation to improve control of sulfurous and other emissions that may affect recovery of certain byproducts was noted. A section on newer technology illustrating hydro-metallurgical techniques that may affect the recovery of minor metals is included.

Jan 1, 1978

Misiman society is matrilineal and despite relatively long contact with Europeans and mining, it retains its traditional consensus style of decision making. Many Misimans at least understand English, and this has encouraged comfortable communication between the people and the company (Misima Mines Pty Limited). Company care in monitoring the environment (mostly using Misiman staff), its policy of maintaining a largely Misiman workforce, and its emphasis on training and safety, have all created an environment compatible with Misiman society. In addition, the company has constructed and/or upgraded community facilities such as the airstrip, roads, the health centre, police station and schools, and has actively promoted local business endeavours. All these initiatives have been accomplished by constant dialogue with the largely Misiman workforce, and with the Misiman people, both before and during implementation. Constant, careful communication, using traditional Misiman consensus methods, appears to be the key to continued community acceptance of the project.

Jan 1, 1991

During an eight month period, January to August 1978, nine bore holes were drilled in the Mikonui River gravels. On account of two rebores required from near bottom, the number of bores is in effect 11. Just on 1300 feet were drilled with an average depth of 120 feet. Depth varied from 102 feet to 133 feet. Penetration on average per hole value, varied from 7.4 to 16.4 feet per day. Gold values were even more erratic. Drill rig used was the Keystone churn drill manufactured locally by the Dispatch Foundary. It is skid mounted and requires a crew of two persons.

Jan 1, 1979

By W. F. Boericke

AT Kellogg, Idaho, J. Fred Johnson is driving the 5000.-ft Hooper Tunnel under contract for the Bunker Hill & Sullivan Mining Co. This was visited by a group of engineers during the recent meeting of the A. I. M. E. at Spokane, who were impressed with several features of the work. An excellent record of advance is being made by the contractor, over 47 ft. being driven in 3 days during October, and 223 ft. advanced in 29 shifts. The size of the tunnel is 8 by 9 ft. The ground is Wallace quartzite and, save for the first hundred feet, stands well and does not require timbering. The grade is held uniformly at 0.5 per cent. Two shifts are employed, with two sets of machine men to the shift. Ingersoll-Rand S-70 drills are used. each machine being set up independently in the heading; 26-30 holes are drilled to the round; using 1 1/4: in. round hollow drill steel. A 7-hole cut is required, and these holes are blasted simultaneously, using 60 per cent gelatine, 12 sticks to the hole. Instantaneous and fire delays of electric detonators are used for the complete round. A feature of the drilling is the use of long carriage drills, necessitating fewer changes of steel, and more time spent on drilling, with less time consumed taking steel back and forth from the face. Of course, this means better blacksmithing so that the drill steel shall stand up for the added footage.

Jan 1, 1930

By G. Zhan, P. Mousset-Jones, G. Danko, J. J. K. Daemen, C. Mezei

Paper presented at the conference Risk assessment in the extractive industries, held in Exeter, 23-24 March 1994, and first published London: IMM, 1994, preprint volume. 18pp., 12 refs. (Originally entitled: Tunnel roof diagnosis using a robotic sensor test bed.) An integral roof diagnosis method is proposed to assist in assessment of risk regarding the stability of an excavation. A Robotic Sensor Test Bed (RSTB) is being developed for the characterisation of roof stability. The sensor test bed consists of a sonic/ultrasonic wave response sensor, a laser surface profiler and a surface temperature sensor. These sensors are mounted on an articulated robot manipulator for performing remote-controlled or fully automated diagnoses. A number of laboratory and field sonic/ultrasonic tests were conducted. A high-energy ultrasonic transducer and an impact device were used to resonate rock slabs. The fracture depths of the slabs were found to be inversely related to the measured resonance frequencies. The agreement between identified and actual dimensions was acceptable. Field tests also showed that loose rock on the surface can be clearly distinguished from solid formation by comparing their wave responses. The robotic laser profiler part of the RSTB was used to measure surface geometry. Different scanning methods are being developed to achieve the fastest and most precise measurements and to provide pertinent information about rock joints and major fractures

Dec 1, 1994

By Alexander Nikolic

The paper presents the foundation design and construction of a landmark urban redevelopment scheme in central London, UK. The scheme comprises the new Tottenham Court Road Underground station, Crossrail interchange box and associated over-site commercial development. The paper focuses on the design, procurement and construction of large diameter bored piles, up to 68m in depth, which form the foundation support system for the over-site commercial development at Denmark Place. The congestion below ground required an intricate foundation design solution which has been a catalyst for developing innovative load transfer arrangements and has resulted in the advancement of pile construction technology in the UK. The foundation system was also designed to cater for the construction of two significant elements of proposed below ground infrastructure. Selected large diameter piles have been constructed within 1.1m of live underground railway tunnels. An innovative D-shaped pile was constructed in a zone subject to particular spatial constraints. The proposed Crossrail tunnels will be bored within 1m of selected over-site development piles. In addition, a 30m deep excavation forming a new escalator box will be constructed in direct contact with the over-site development piles. The stakeholder engagement process is described together with the foundation design development and buildability assessment. The benefits from early collaboration between the designers and specialist contractors are highlighted. From an analytical design perspective, the entire foundation construction sequence was modelled in detail in order to assess the soil structure interaction and any potential adverse effects on existing elements of underground infrastructure. The results from the three dimensional numerical modelling simulation are compared with field monitoring data.

Jan 1, 2011

By Craig C. Johnson

The purpose of this effort was to investigate the feasibility of employing a piezoelectric transducer for seismic communications applications in mine environments. The transducer, a government furnished device incorporated a high Q, spring-mass resonator to load the air side of the piezoelectric crystal. The resonant frequency was seismic load dependent and fell in the range of 300 to 340 Hz. The effort included a mathematical analysis of the transducer, with corroborative laboratory tests, together with actual communications experiments performed first in an open-formation limestone quarry and finally in an operating iron mine. This work showed that the transducer could be coupled efficiently to hard, competent rock media with power conversion efficiencies of 70 to 80 percent (electrical to mechanical) in typical installations. In the iron mine, when radiating peak power was about 30 W (acoustical) in a gated pulse mode, signals were received at a distance of 760 ft through a massive rhyolite porphyry formation. This represents a 15% radiation efficiency with an input of 200 watts. Despite the high ambient noise level due to operating mine machinery, a signal-to-noise ratio of about 20 dB was achieved using a very narrow band filter to process the received signal, and a data rate of about two pulses/sec was demonstrated.

Jan 1, 1972

By W. Pulles

Mining can adversely affect water quality and poses a significant risk to South Africa?s water resources. Proactive management of environmental impacts is required from the outset of mining activities in order to reduce this risk. Major strides have been made over the last 7 to 8 years, by both the Department of Water Affairs & Forestry (DWAF) and the mining industry, in developing strategies and management plans for the effective management of water within the industry. This has largely been achieved through the development of joint structures where problems have been discussed and addressed through cooperation. This process, which was started around 1991, has continued through to the present time. The mining sector management strategy has been developed at a number of different levels as follows: ?A detailed Management Plan, that sets out strategic objectives, broad strategies and functional and organizational arrangements. ?Operational Guidelines, that define and document specific operational procedures. ?Technical Guidelines, that define and document best practices for pollution prevention and impact minimization from mining operations. The Technical Guidelines consist of Best Practice Guidelines (BPGs) and Regulations.

Jan 1, 1999

By Ammar Henchiri, Godfrey McDonald

"Breakwater Tunisia S.A.’s Bougrine mine is located in a semi-arid region of Tunisia characterized with Triassic salt domes. Due to extensive agricultural land-use in the mine area, a zero-discharge tailings facility design and high water recycling rates to the concentrator were chosen to minimize the environmental impact to the surrounding area. The process water supply has an accumulation of naturally occurring salts due to high evaporation rates and the need to recycle 70% of the process water. The elevated salt content of the process water had an adverse effect on the efficiency of the flotation reagents, which led to the production of lower quality zinc concentrate.The impact of the water salinity on the zinc concentrate quality was documented by extensive laboratory testing. A feasibility study was prepared and a decision was made to install a reverse osmosis plant for desalination of the process water. A plant was constructed during 2000 which currently supplies up to 85 m3/hr of de-mineralized water, equal to approximately 45% of the total process water requirement. The salinity of the process water decreased from about ten to twelve grams per litre before installation to less than three grams per litre. Together with minor modifications to the concentrator circuit, Breakwater Tunisia has increased the zinc concentrate grade from 50% zinc to 55% zinc without compromising the zinc recovery rate of approximately 84%.This paper discusses the successful installation of a reverse osmosis desalination plant that allowed Breakwater Tunisia to improve the grade of the Bougrine mine zinc concentrate and thus increase the net smelter return.INTRODUCTIONBreakwater Resources Ltd., through a wholly owned subsidiary, Breakwater Tunisia S.A., acquired the Bougrine underground mine and related assets in September 1997. During the winter of 1997/1998, the company rehabilitated the mining equipment, modified the concentrator circuit, developed a new mine ventilation system and prepared a new mining production program. The mine was reopened on May 2, 1998 and was in commercial production as of June 1, 1998."

Jan 1, 2003

By Wang Xuguang, Zhang Xiaozhi, Li Guozhong, Xiong Daiyu

The emulsion explosive is a new kind of water-based industrial explosives that was developed at the end of 1960s. In the 1970s, BGRIMM invented EL-series emulsion explosive that created a new era of water-based industrial explosives technology and products in China. From single type to varieties, the perfect BGRIMM emulsion explosives technology has been formed, which consists of 9 series, over 30 types explosives and related production equipments and processes such as cap-sensitive rock emulsion explosive, opencast emulsion explosive, coal permitted emulsion explosives, low-temperature-resistant emulsion explosive, high-temperature-resistant emulsion explosive, high power emulsion explosive, bulk emulsion explosive for loading truck and powder emulsion explosive. From the early 1990s, BGRIMM successfully developed opencast emulsion explosives and the computer controlled continuous production line of small-diameter cap-sensitive emulsion explosive which raised emulsion explosive production technology of our country to a new lever. With the successful development of powder emulsion explosive and related computer controlled continuous production line, on-site mixed emulsion explosive and loading truck as well, the category of industrial explosives is getting more complete and reasonable. This paper pres ents the history, achievement and development of BGRIMM emulsion explosive technology, also forecasts the future of linked technology.

Jan 1, 2003

By W. G. Pariseau

This contribution describes rock mechanics features of the Davis Cavern at the former Homestake Mine in Lead, South Dakota, U.S.A. The mine is located in the northern Black Hills of South Dakota. In 2003 and again in 2008, the mine site was recommended for development as a national Deep Underground Science and Engineering Laboratory (DUSEL) in cooperation with the Sanford Underground Science and Engineering Laboratory under the South Dakota Science and Technology Authority (SDSTA). The original Davis Cavern was excavated about 9.1x16.8x9.7 m high (30x55x32 ft high) in 1965 (Mitchell 2009) at a depth of 1,478 m (4850 ft). The purpose of the cavern was to house apparatus for detecting solar neutrinos. The experiment ultimately proved successful and earned R. Davis a share of the 2002 Nobel Prize in physics. Recently, a new experiment (LUX=Large Underground Xenon detector for dark matter particles and WIMP's=weakly interacting massive particles) was proposed for the Davis Cavern that required an increase in height of 2.4 m (8 ft). For many years, the Homestake gold mine was the deepest operating mine in North America. Development extended to the 8000 Level (2,438 m). The mine closed in 2003. Pumps were shut off and the water level rose to the 4350 Level, about 150 m (500 ft) above the Davis Cavern. Some six years later after selection for DUSEL proposal development by the National Science Foundation (NSF), access to the 4850 Level and the Davis Cavern was regained. Pumping has lowered the water level to well below the cavern floor. Figure 1 shows the layout and location of the Davis Cavern (Cavity). Detector tank, supporting steel, and so forth were subsequently removed. The cavern was re-supported and new access was developed. By August, 2010, 13,000 ft3 had been removed during enlargement and renovation of the Davis Cavern. Figure 2 shows the detector tank under construction in 1965.

Jan 1, 2012

By Jacob Carr, Christopher C. Jobes, Chenming Zhou, LaTasha R. Swanson, Jennica Bellanca, Jingcheng Li

Magnetic proximity detection systems (PDSs) are used with continuous mining machines (CMMs) to protect miners from striking and pinning accidents. Generators are used in a PDS to create magnetic fields covering the space around a CMM. The PDS determines the proximity of a miner relative to the CMM based on the magnetic flux density detected by a miner-wearable component (MWC) and simultaneously alerts the miner and stops the motion of the CMM if the miner is within a proximity that creates a striking hazard. A stable magnetic field is essential to the accuracy of the proximity calculations performed by the PDS. This paper presents the results of a systematic study of the magnetic influence of two types of steel structures found near a CMM— the body of the CMM itself and the wire mesh used for roof and rib control. The results show that the steel of the CMM body can change the magnetic field distribution and also alter electrical parameters of a PDS by changing its generator current. The study also shows that, depending on the distance between the wire mesh and a generator, the magnetic field can also be altered.

By Jacob Carr, Christopher C. Jobes, Chenming Zhou, LaTasha R. Swanson, Jennica Bellanca, Jingcheng Li

Magnetic proximity detection systems (PDSs) are used with continuous mining machines (CMMs) to protect miners from striking and pinning accidents. Generators are used in a PDS to create magnetic fields covering the space around a CMM. The PDS determines the proximity of a miner relative to the CMM based on the magnetic flux density detected by a miner-wearable component (MWC) and simultaneously alerts the miner and stops the motion of the CMM if the miner is within a proximity that creates a striking hazard. A stable magnetic field is essential to the accuracy of the proximity calculations performed by the PDS. This paper presents the results of a systematic study of the magnetic influence of two types of steel structures found near a CMM— the body of the CMM itself and the wire mesh used for roof and rib control. The results show that the steel of the CMM body can change the magnetic field distribution and also alter electrical parameters of a PDS by changing its generator current. The study also shows that, depending on the distance between the wire mesh and a generator, the magnetic field can also be altered.

By Charles H. Jacoby

The solution mining of evaporites has a history of approximately 5,000 years. The insitu leaching of metalliferous ore will have many of the same characteristic problems which have confronted industry for years in the production of evaporite minerals. Basically we will be converting the less soluble forms of valuable metals into their more soluble salts and producing these in much the same manner as, for example, sodium chloride. There are a number of problems which we are faced with that are more complex and complicated and, therefore, will require a higher degree of sophistication than previously employed. One of our most important undertakings will be the clearcut definition of the problems involved. While a great deal of expertise can be drawn from the solution mining of evaporites and the oil industry, problems peculiar to the hydrometallurgical field will need to be solved. One of these is the introduction of permeability into an impermeable rock so as to expose the sought after values of metals which by volume are infinitesimal when compared with sodium chloride, potash or other type water soluble mineralization. After establishing this permeability which will be miniscule when compared to a solution cavity, there will be the maintenance of this permeability. In general, salt deposits are of a somewhat uniform chemical composition and thus their chemistry was relatively simple. Each metalliferous ore body is somewhat unique in its chemistry and will need to be treated accordingly.

Jan 1, 1974

By S. Kelebek

DETA exhibits a highly selective depressant action on pyrrhotite without adversely affecting the collectorless flotability of pentlandite and chalcopyrite in nickel-copper ores of the Sudbury region. A simplified Eh-pH diagram has been constructed to illustrate the extended stability of elemental sulphur and to explain the collectorless flotation of pentlandite and chalcopyrite. Cu and Ni ions, which are known to exist on the surface of pyrrhotite, promote the flotation of this mineral whether a collector is present or not. Thermodynamic calculations indicate that the action of DETA involves the sequestration of Cu and Ni ions from surfaces under a wide range of redox conditions; analysis of flotation test filtrate indicates as much as a 20-fold increase in the concentration of Ni and Cu ions. It appears that DETA may enhance the self-hydrophobicity of chalcopyrite and pentlandite by exposing more of the sulphur-rich surface sites for bubble contact in flotation. There are various possible explanations for its depression of pyrrhotite

Jun 18, 1905

By Rapheal Trousselle

For over 5 years, Davey Bickford has been developing and testing an electronic detonator blasting system. These new-technology detonators provide more accurate timing than conventional systems that rely on the combustion speed of a pyrotechnic composition.

Jan 1, 1997

By T. R. Roy

A prediction model, developed by Central Mining Research Institute (India) for evaluation of fire risk rating of underground coal mine panels in bord and pillar working in respect of their proneness to spontaneous heating, is presented in this paper. The concept used in this model is innovative and user friendly. This model may be applied to a panel where extraction is carried out using any of the techniques: i) depillaring with formation of small pillars as final operation, ii) extraction by broadening of galleries, iii) depillaring with hydraulic sand stowing, and iv) depillaring with caving. Here, major fire risk parameters are short-listed and divided into three broad groups in accordance with the nature of their contribution to the spontaneous heating of a mine panel. The paper describes the procedure for estimating the fire risk rating of individual groups using separate objective type models developed for this purpose. Then it evaluates the overall fire risk rating of the panel by combining the fire risk ratings of all the three broad groups. The model is tested with the field data collected from different collieries spreading across the country and with the laboratory data for critical assessment of fitness. Keywords : prediction model, fire risk rating of panel, spontaneous heating of coal, underground panel, bord and pillar working.

Jan 1, 2003

The Khanong supergene-enriched copper resource, (~23 Mt at 3.0 per cent Cu), is one of several resources recently discovered in the intrusive-centred, sediment-hosted Au-Cu Sepon mineral field located in southern Lao PDR. The unusual style of hypogene mineralisation and unique set of conditions have resulted in the development and preservation of a supergene-enriched profile in this subtropical climate. Hypogene sulphide-rich mineralisation replaced calcareous cataclastite (fault rock) developed in the flat-lying, extensional, Khanong Fault. Spatially, the hypogene mineralisation was immediately out board of the skarn û hornfels Cu-Bi front and in board of sediment hosted Au-(As-Sb) mineralisation in a zoned intrusive-centred hydrothermal system. In situ supergene enrichment of the sulphide protore has resulted in a high-grade chalcocite-clay zone (~10.3 Mt at 4.6 per cent Cu) overlain by leached limonite-clay. A very high-grade in situ to exotic limonite-clay Cu-oxide-mineral zone is locally developed above impermeable dolomite at the base of chalcocite-clay zone. Exotic Cu-Mn-wad mineralisation developed for up to 1 km down the hydraulic gradient from the chalcocite-clay zone. Unique supergene enrichment conditions have resulted in the high-grade Khanong Cu resource in a subtropical weathering environment. The base of the currently active supergene profile coincides with the base of a flat-lying, pyrite-rich fault rock, dipping parallel to the hill slope, maximising Cu enrichment. Meteoric water has been channelled along subvertical faults and narrow horizontal subsurface zones. Low permeability of the fault host rock and footwall rocks has controlled the low volume and slow movement of groundwater required for supergene enrichment. Erosion has been slowed by the resistive ironstone and limonite-clay layer at surface, which assists in preserving the gentle slope over the chalcocite-clay zone.

Jan 1, 1999

By G. A. Grandy, P. F. Thomas, C. D. Danecki

When considering the mill drive system for a grinding application, a large number of questions must be answered. Depending on the mill size and type, the mill can be driven by several configurations of drive systems: a single low-speed motor connected to a pinion driving a ring gear, two low-speed motors connected to two pinions and driving a ring gear, or a gearless motor mounted directly. In addition, a gear drive system can have a reducer placed between a high-speed motor(s) and pinion(s) or a power path splitting pinion stand. In some designs the reducer is integral with the pinion stand driven by a high-speed motor. The technical and commercial implications of several mill drive options are presented. Initial cost, cost of installation, cost of commissioning, and cost of operation and maintenance are presented for each drive option considered. The impact of each drive system on the design, cost and operation of the overall plant electrical system is discussed. Also, consideration is given to mill drive availability, and the potential cost resulting from delays in plant production.

Jan 1, 2001

M.S. Azun I have many objections to the content of the author's paper. Before discussing it, however, I would like to repeat the property of semivariogram function. Second order stationary properties of regionalized variables (ReV's) such as semivariogram function y(h) are perfectly known in geostatistics. Also, the kriging equations in the language of mathematical statistics using second order stationary properties are well understood. However, the way to use the sample (estimated) semivariogram function in any one of the kriging procedures is vague. The sample semivariogram function is given as follows: [ ] where N is the total number of samples, Xi is the sample value at the i - th location, Xi+h is the sample value at the i + h - th location, and h is the distance among the samples. An estimation variance of sample semivariogram function of first lag is smaller than that of higher order lag. The theoretical semivariogram function reaches the variance of samples asymptotically. But this is not easily observable because of the larger variation involved in the estimate of semivariogram function. In general, an estimation procedure is done for h = 0, 1, 2, up to the greatest integer less than N/2, even though sample semivariogram function can be computable through N-1. After estimating semivariogram function, the critical question of how to model sample semivariogram function arises. As seen in the above equation, sample semivariogram function is discrete and can be smoothed by the model being selected. Therefore, modeling of sample semivariogram function is the most important step in geostatistics. It not only smoothes a discrete function but also affects the results of the kriging procedure. When the only aim is to model the semivariogram function, which is the basic point of the author's paper, one can employ any fitting techniques, such as curve fitting, or any arbitrary functions, which are called submodels in the paper. The term "arbitrary function" is used rather than "submodel" because there is no basic understanding of developing them. The author suggests that the sum of those submodels can also be used for the modeling of sample semivariogram function. The combination of any arbitrary functions brings many problems instead of giving an insight of the domain structure considered. The author used two arbitrary functions and the nugget effect in response to sample semivariogram function (Fig. 10). For the same example, he stated that the parameters involved in the mixed arbitrary function model can be accepted when the discrepancy between sample semivariogram function and the model is small visually. For verifying the fitting behavior of any selected model, one should not be contented with the visual satisfactory. Some statistical measure such as goodness of fit has to be used. The author's practice is no more than an exercise in curve fitting without any fundamental understanding or conceptualization of the underlying physical mechanism. Furthermore, the selection of any model is not an easy task if the purpose is the search for the "best" response to the observed second order properties of ReV's. I suggest that the Markovian model (Azun, 1983), on the basis of a theoretical understanding of underlying mechanism, which gives more information about the occurrence of regionalized variables, is used to respond all properties of ReV's. There are a lot of problems for modeling of one-dimensional sample semivariogram function. Thus, it is not appropriate to go to higher order dimensional sample semivariogram function modeling. In the meantime, I would recommend that one can connect the values of standardized sample semivariogram function rather than simple values of semivariogram function in the two-dimensional estimation. The standardized values can be computed in dividing the semivariogram function value by the number of sample pairs involved in each lag regardless of the directions. In conclusion, geostatistics is an interdisciplinary area in mining that uses the principles of mathematical statistics. Thus, it should not violate any probabilistic and statistical rules. When Matheron was developing the theory of geostatistical study in the early years of geostatistics, many mining people had a reservation accepting the geostatistical tools. However, this does not mean that we, the geostatisticians, might try to convince those people using some "strange" tools or rules as some authors implied (Baafi and Kim, 1984). Instead, we have to develop and explain the geostatistical tools staying only in the framework of statistical concepts and properties. References Azun, M.S., 1983, "Stochastic Process Modeling of Spatially Distributed Geostatistical Data," Columbia University, Ph.D. Thesis. Baafi, E.Y., and Kim, Y.C., 1984, "Discussion - Comparison of Different Ore Reserve Estimation Methods Using Conditional Simulation," Mining Engineering, Vol. 36, No. 3, p. 280. Reply by J.M. Rendu The interactive method proposed by Rendu allows practitioners to develop semivariogram models that take into account not only the numerical information obtained by sampling, but also highly significant additional information that often cannot be quantified. The geology of the deposit - including hypotheses concerning its genesis, sampling methods, assaying methods, and mathematical methods used to calculate the semivariograms - all have an influence on the numerical results obtained and on how these results should be interpreted. If all the information concerning the spatial distribution of values in a mineral deposit was contained in the sample values, it could be argued that statistical techniques alone would produce optimum models. However, this is rarely, if ever, the case. Methods that allow the user to take into account his experience and his geologic understanding of the deposit should not be rejected for the sake of theoretical statistical purity.

Jan 11, 1985