The leaching of heaped Caliche minerals represents a valid alternative for the saltpeter extraction, giving good recovery levels with excellent economic projections and technical results when compared with existing technology. This study reports on experimental tests of the leaching of this mineral in columns in which we determined the recovery of nitrate and magnesium at different heights through the bed of the mineral. The columns were sampled at three different heights, recovering the strong solution from sample ports at each height and calculating the recoveries of the target materials at each height. These variables were analyzed as a function of time and irrigation ratio, thus obtaining empirical kinetic expressions. A simple mathematical model was constructed which represented the leaching process for the solutes, considering the variation in height of the bed of the leached mineral. The model showed a good fit for predicting the concentration of nitrate and magnesium. (c) 2007 Elsevier B.V. All rights reserved.