Methods of testing bentonite clays as a raw material for the production of pellets are evaluated. A comparison is made between two similar methods – testing based on swellability and testing based on the swell index. It is shown that the quality of clays cannot be properly evaluated based on the obsolete method of swellability and should instead be judged by the swell index on the basis of the amount of time that the clays are in contact with the concentrate. The intrinsic properties of clays are realized to the greatest extent by taking this approach. Arguments are presented in favor of jointly evaluating the properties of bentonite based on the swell index and the Enslin number.