Geometallurgical sampling protocol validation by bulk sampling in a sheeted vein gold deposit

Abstract

Sheeted vein gold deposits are characterised by multiple sub-parallel veins and often free milling gold. Variability in gold grade and recovery parameters are enhanced by poorly designed sampling and testwork protocols. Poor quality samples generally equate to an enhanced nugget effect. A sample can be described as being representative when it results in acceptable levels of bias and precision. Total sampling variability can be quantified by the relative sampling variance, which measures the total empirical sampling variance influenced by the heterogeneity of the lot being sampled under the current sampling/testwork protocol. Effort should be made to minimise the relative sampling variance through Theory of Sampling and QA/QC application. This contribution reports on a case study, which exemplifies how gold grade and recovery data can be gained from a well-designed and planned drilling, sampling and testwork, and bulk sampling programme. Results across historical resource drilling; geometallurgical drilling; laboratory assay/testwork, geometallurgical modelling and a bulk sampling/pilot processing study are discussed. A whole-core entire-sample testwork protocol was used to acquire fit for purpose gold grade and recovery data for inclusion into a pre-feasibility study reported in accordance with The JORC Code (JORC, 2012).