Abstract
Bentonite is widely used for various industrial fields. The resistivity of bentonite is generally very low because it contains a lot of smectite which has high conductivity. It means that the electrical and electromagnetic methods are suitable for bentonite exploration. In order to confirm it, we measured the resistivity with other physical and chemical properties of the samples of bentonites and surrounding rocks of the Kawasaki and Tsukinuno bentonite mines. The resistivity is well correlated with the water content and the free swell. Except the rocks containing zeolite, the resistivity is also related to the cation exchange capacity (CEC). A good correlation was found between the resistivity and the methylene blue adsorption that is used as an index of the quality of a bentonite. These facts indicate that electrical and electromagnetic surveys are effective for subsurface bentonite exploration and evaluation.
