This paper shows a methodology for implementing the optimization algorithm Lerchs - Grossmann in a coal deposit under uncertainty in the price in the market. The methodology consists in make different simulations with optimization algorithm Lerchs - Grossmann, varied ore price in each of these simulations, choosing the price needed to perform the simulations in the current cycle before. Economic analysis was performed for each of the simulations with the aim of fi nding exploitable reserves and the net present value (NPV).