This paper aims to present the results of several laboratory tests carried out to characterize two samples of bentonite clay largely used on the Geosynthetic Clay Liner (GCL) Brazilian industry for sanitary landfill liner application. The difference between the samples was basically physical: one of them was grainy (Sample A) and the other was in powder (Sample B), and both of them were obtained by the same supplier. The performed tests to differentiate their properties were, natural humidity, grain size distribution, specific weight, Atterberg limits, swelling index, free expansion, swelling pressure, consolidation properties and coefficient of permeability. With these results it was possible to calculate their colloidal activities and minimum permeability coefficient when the sanitary landfill reaches saturation. The presence of clay on the samples was practically identical: 74% and 78%, respectively and their specific weight resulted in 2.87 g/cm³ (sample A) and 2.79 g/cm³ (sample B). The results of the conducted experiments showed that the powder sample (B) had slightly better properties in comparison to the grainy sample (A) when used as a liner. Its colloidal activity, which is an indicative of the expansive potential of the bentonite, and is calculated by the relation between the plasticity index and the percentage of clay present in the sample, was 3.7 (bigger than the result of the sample A, which was 3.6). The swelling tests results pointed to the same direction: only the powder sample surpassed the reference standard, reaching 25 mL/2g. Due to its good performance, only the sample B was used as a reference to calculate the coefficient of permeability on the saturated condition. When the disposed residue reaches a height of 10 m, its calculated tension is 125 kPa and the coefficient of permeability results in 1.8x10^-9 cm/s.