Estimating sampling and analytical errors of multiple source mine output blended into shipping product

Abstract

Most internationally traded iron ore resources are derived from multiple mine sites, transported to a port facility where they are blended and possibly further processed before shipping. Provided the proportion of contributions varies over a number of shipments, an estimate can be made of the bias introduced by mine site sampling, analysis and materials handling systems, using zero‐intercept multiple linear regression. Further regression applied to the residuals allows the error variances for the source mines to be estimated. Various sampling strategies are used by the industry. All have shipment loading sampling on which payment or at least provisional payment is based. In most cases, sampling pre‐stockpile is used at mine sites to verify estimated production grades. Train grades are estimated from mine stockpile grades and in some cases train grades are verified by port input sampling. The methodology used is presented in this paper. Simulated data have been used and do not reflect the actual performance of any operator.