Issue 3, p. 7 (2014)

  Article

Illusory reconciliation: compensation of manual sampling errors

  • Thammiris Mohamad El Hajj  
  • Ana Carolina Chieregati
  • Luiz Eduardo Campos Pignatari
Department of Mining and Petroleum Engineering, University of São Paulo, Brazil

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Yamana Gold Inc., São Paulo, Brazil

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 Corresponding Author
Department of Mining and Petroleum Engineering, University of São Paulo, Brazil

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In the mining industry, reconciliation can be defined as the practice of comparing the tonnage and average grade of ore predicted by the geological models with the tonnage and grade generated by the processing or metallurgical plant. This practice is of increasing importance, since, if correctly executed, it allows the reliability of short-term planning to be improved and the mining and processing operations to be optimised. However, the usefulness of reconciliation relies strongly on the quality of the input data, which is generated by many different sampling methods across the industry. In fact, successful reconciliation can be illusory—errors generated at one point of the process can be offset by errors generated at other points, resulting in apparently excellent reconciliation. Such a situation will in fact also hide compensating biases in the system that will, unavoidably, surface some other day. When this happens, sampling errors are masked and may lead to an erroneous appreciation of the reconciliation system as a whole, which results in serious consequences for the mine operation, especially when reaching poorer or more heterogeneous areas of the deposit. Since valid estimation is only possible with TOS-correct sampling practices, the reliability of reconciliation results depends critically on the representativeness of the samples that generated them. This contribution a summary of an analysis of the manual sampling practices carried out at a copper and gold mine in Goias, and proposes a more reliable sampling method for reconciliation purposes. Results show that the apparently excellent reconciliation between the mine and the plant was in fact illusory; here a consequence of accidental compensation of many errors due to sampling practices for short-term planning.

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