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Show grades and reserves, which is directly linked with the control of sample data reliability and proper use. It is clear from these statistics that neither the potential benefits of better sampling and sample grade processing, nor the actual quality of the grades derived from the samples, are usually obvious to the project evaluator. The problem of controlling the reliability of mining samples therefore is both economically more important, and technically more difficult, than would appear at first glance, and only the proper use of Sampling Theory offers some protection against the negative impact of this unfavorable, albeit fairly general, situation. on improper predictions of grades and reserves, which is directly linked with the control of sample data reliability and proper use. It is clear from these statistics that neither the potential benefits of better sampling and sample grade processing, nor the actual quality of the grades derived from the samples, are usually obvious to the project evaluator. The problem of controlling the reliability of mining samples therefore is both economically more important, and technically more difficult, than would appear at first glance, and only the proper use of Sampling Theory offers some protection against the negative impact of this unfavorable, albeit fairly general, situation . BENEFITS TO BE EXPECTED It would most likely be impossible to inventory and describe all the benefits that good sampling control may be able to generate. However, here are a few of the benefits that can be expected from the study of the sampling parameters particular to a given project: Field sampling procedures: proper understanding of the theory allows the early detection of sampling biases, the design of adequate sample collection procedures, the control of the representativeness of the primary sample, the economic optimization of the amount of sample to be taken. Segregation phenomena are a major negative factor when sampling broken ore. Sampling theory addresses segregation, and offers methods of reducing its impact on the reliability of the samples. When the primary samples are later prepared in the preparation laboratory, they are subjected to a cascade of crushing and secondary sampling (mass reduction) operations, each one of which can potentially jeopardize the reliability of the initial sample . Sample preparation protocols can be optimally designed using Sampling Theory so that the overall effect of primary and secondary sampling operations are kept below an acceptable, preset, threshold of uncertainty. With the resulting improved drill hole data reliability, the following hidden benefits will be obtained: improved, less nuggetty variograms, improved data analysis and grade data interpretation resulting in improved ore grade predictions, economic ore delineation, hence improved mine planning and design; improved drill hole grade correlations, better understanding of the nature of the mineralization; proper assessment of the real 'nugget effect'; improved understanding and handling of grade outliers. Improved control of mining and ore process testing: better design of sampling procedures for the testing of bulk mining as well as metallurgical processes, resulting in lower decision risk levels; better informed conclusions on the results of the tests, resulting in an improved assessment of optimal mining method and ore treatment process. Mineralogy: the experimental study of the ore sampling parameters often give additional insights into metal/mineral grain sizes, and the mineralogical nature of ore grades. Better detection of systematic biases at the assay laboratory. Improved grade control through more reliable data, with measurable benefits in terms of produced grade and accuracy of the selection, and in some instances, improved cutoff grade policy (detection of warning signs when ore delineation at current cutoff grade is illusory). At the metallurgical plant level, control of the sampling procedures and equipment, leading to improved metallurgical balances and reduced mine-mill variance problems. Improved commercial ore sampling, improved ability to resolve commercial disputes. |
