Sampling of the mineralised tailings dumps–case study of the Mount Morgan project, central Queensland, Australia

A new sampling protocol was developed to overcome the difficulties in sampling viscous unconsolidated mine tailings. This new procedure involved collection of the entire drill sample from the drill rig cyclone, (approximately 15 kg) which is delivered to the sample preparation laboratory where it was dried, crushed and subsampled. Comminution and subsampling parameters were deduced by estimating the fundamental sampling error and construction of the sampling nomogram. Based on this analysis, the optimal protocol was designed as follows: Drying the entire 15 kg sample at 60°C Reporting of sample mass and free moisture content Crushing of entire sample to 90% passing − 2 mm Use of a rotary sample splitter to collect a 3 kg subsample Pulverising the entire 3 kg subsample to 74 µm Collecting of a 50 g aliquot for fire gold assay with atomic-absorption finish The quality of sampling was rigorously monitored using sample duplicates, blanks and standards, which have confirmed the accuracy and repeatability of the data. Correlation between field duplicates and original samples was high at 98% with a precision error of 19.8%, which is considered excellent for gold mineralisation. The high quality of the data was important for the accurate evaluation of the project, and enabled the confidence in classifying a significant part of the mineralised endowment as an indicated resource. © 2017 Institute of Materials, Minerals and Mining and The AusIMM.