Variography applied to particle size evaluation for particle sorting


Prof Bern Klein, Prof Gustavo Sánchez, Mr Santiago Seiler

In the mining industry, one of the main challenges is the proper identification of ore and waste. Due to the large scale that is commonly used for resource modelling and mine planning, waste or barren material may be introduced as ore to the process, and ore may be sent to the waste dump. The addition of a pre-concentration stage, such as mineral sorting, prior to milling has shown to have a significant effect by reducing dilution. In this work, variography was used to analyze the surface distribution of two samples of a porphyry copper ore. The variogram is a widely used tool which has been proposed to describe the spatial correlations of punctual spatial observations. The objective of this tool is the pattern evaluation of a given variable in space. The results of the variography analysis were applied to evaluate how the particle size can affect the liberation of waste and, therefore, the particle sorting performance. The surfaces of the rocks were scanned using a XRF handheld device and the data was analyzed in two dimensions. It was observed that copper was concentrated in vein bands, which is consistent to the mineralization pattern present in the two samples analyzed, whereas copper is mainly in veinlets or veins. This result may indicate that the optimum particle size for sorting is equal to the band width. However, there are some conditions that can affect this, such as the vein densities, in other words, the distance between veins.