Orientation Study of the Efficiency of Bulk Leach Extractable Gold (BLEG) Assay Method on Hwinibutre and Benso Ore Samples at Golden Star Resources

Abstract

Al-Hassan S. & Abusah R. K.

The Hwini-Butre and Benso (HBB) concessions were acquired by Golden Star Resources (GSR) as part of their takeover of St. Jude Resources (SJR). Originally exploration samples (RC and DD) were analysed by 50g Fire assay method. The low repeatability of fire assay data from Hwinibutre and Benso deposits has created a great concern as it could severely impact on resource estimates. Considering an alternative method to improve the analytical reproducibility of assay data, GSR wishes to resort to analyzing 1000g of sub-samples by Bulk Leach Extractable Gold (BLEG) assay method. One challenge is that GSR is not sure about the efficiency of the BLEG method on the samples. In an attempt to verify the suitability and efficiency of the BLEG analytical method based on the accelerated cyanide leach extraction, 1kg each of RC samples and duplicates representing 10% of the Benso and Hwinibutre drill sample populations were subjected to BLEG orientation study to investigate for theleachability and efficiency of the BLEG method on the Hwinibutre and Benso ore samples. Furthermore, BLEG and fire assay analysis were carried out on selected samples and duplicates to investigate the Au grade reproducibility of the assay methods on ore samples. The Bulk leach orientation study revealed that their ore samples were leachable with gold recovery levels ranging between 96% and 99.6% for leach time between 8 and 12 hours. The study also indicated that the BLEG assay method was a more suitable method for the Hwinibutre and Benso ore samples than the fire assay method. The cost of the BLEG assay per sample is lower than that for fire assay. It is therefore recommended that, for better reproducibility and assurance in reliability of Hwinibutre and Benso samples, the BLEG method should be preferable.

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