Future challenges and research: theory of sampling (TOS)

Importance of good sampling practice throughout the gold mine value chain

“…Distribution heterogeneity of a given lot is governed by CH, the spatial distribution of fragments and the lot shape, thus leads to GSE. From a practical perspective, GSE cannot be measured, but may have a material effect on the total sample error (François-Bongarçon 2014;Pitard and François-Bongarçon 2011). It is controlled by accumulating many small increments to form a composite sample.…”

“…Beyond the FSE equation, TOS provides important guidelines for reducing the sampling errors (Table 1). It is here to stay, though there is still much to do in context of research, communication and education (François-Bongarçon 2008, 2015; Pitard, Esbensen and Paoletti 2015).…”

“…Those issues that contribute to the GSE and ISE include: poor disintegration of gold particles during pulverising often lead to smearing and/or the coating of sample preparation or testing equipment leading to PE (Dominy and Petersen 2005; Pitard 2009) high contrast between the densities of gold and gangue minerals promote segregation once liberated, which leads to GSE (François-Bongarçon 2015; Pitard 2009) and bias during diamond drilling relates to the plucking of gold particles from the core surface as a result of the drilling process (Dominy 2014a; Pitard 2009), which leads to a negative grade bias (EE). Core sawing can also lead to gold loss in the cuttings (PE). These problems can be overcome through the use of larger sample and assay charges, and careful procedures to minimise sampling errors.…”

“…high contrast between the densities of gold and gangue minerals promote segregation once liberated, which leads to GSE (François-Bongarçon 2015; Pitard 2009) and…”

Ore heterogeneity case study and optimisation of sampling protocols for the Central Jordan Uranium project

“…Exponent alpha in equation (3) was first determined using an experiment consisting of calculating single stage experimental sampling variances from a series of samples at various comminution sizes, namely pulps passing 66.6, 2, 0.475 and 88 μm. Analytical error variances were previously modelled as described in Francois-Bongarcon (1998) and were subtracted. The following model was experimentally fitted by asymptotic analysis to pairs of pulp duplicates † The detailed calculation of single stage variances is too lengthy to be included in this paper and in fact relates more to the general methodology used here.…”