The object of this work is to propose a software developed with the aims to quantify the presence of montmorillonite in basaltic rocks. The method is based in the tinction of the montmorillonite in thin section by means of methylene blue. The effectively of the method has been testes with samples of known quantity of montmorillonita. There have been used 3 samples of known ASR behavior and previously study by conventional standard test like: The accelerated method of the mortar bar; the petrographic method and the chemical method.