Three A.P.I. day standards--Macon, Georgia kaolinite (H-4); Clay Spur, Wyoming montmorillonite (H-26); and Fithian, Illinois illite (H-35)--were disintegrated mechanically and/or chemically in order to determine the most applicable disaggregation technique for argillaceous rocks (e.g., shales, bentonites). X-ray diffraction data and scanning electron microscope observations indicate separation of clay standards in the presence of a Na 2 CO 3 solution or methanol is less destructive than are dry techniques. A probe-type ultrasonic device is considered an effective tool for disaggregating all three tested clays. Three diagrams showing a linear relationship between the relative x-ray peak intensity and disaggregation time are presented to allow selection of the most applicable method for various types of clay constituents.