The metallurgical recovery rate varies little in space because the recovered grade closely follows the total in situ grade, giving a stable ratio that is insensitive to the chosen calculation method, additive or not, except when calculations are made at the scale of the entire deposit. For heap leaching, the metallurgical recovery rate shows significant spatial variations due to the high variability of the solubility as it was calculated at the time of the study. Before mine production begins, laboratory experiments are performed in order to forecast the flotation performance of the ore that will be processed. Laboratory experiments are carried out to evaluate the performance of the process. To this end, leaching columns of several meters high are used, containing ore in which the acid diffuses at a speed comparable with the one supposedly involved in the heaps.