Clay and shale samples can be impregnated while retaining their natural moisture. Carbowax 6000 (Carbide and Carbon Chemical Co.), a waxlike high molecular weight polyethylene glycol compound was used. This wax is not isotropic and reacts with some clay minerals. After impregnation the samples can be cut and thin sectioned using kerosene instead of water. The kerosene is removed before the slice is mounted on a glass slide. Samples required for sectioning should be collected moist in the field and well wrapped immediately in aluminum foil to prevent their drying out.