Abstract: Beginning with the work of Ladd in 1898, much has been written about the kaolins of the Southeast, with maximum coverage on the deposits of greatest economic value. Early studies were, of necessity, general in nature but also contain excellent detailed descriptions. In the past 15 years increased demands for kaolins to meet specific requirements have resulted in a large amount of detailed research, much of it unpublished. This paper attempts to review the available information placing emphasis upon the geologic and mineralogical data and the interpretation thereof with respect to the occurrence, detailed character and variability, and probable origin of the clay deposits.
The commercial deposits of kaolin clay discussed herein lie throughout the sands of the Upper Cretaceous Tuscaloosa formation and are localized in a narrow belt along the southeast edge of the “fall line” from Macon, Georgia, to Aiken, South Carolina. The kaolin lenses are irregular in shape, size and purity, ranging from a few feet to a mile in length, and up to 50 ft in thickness. Variability within the lenses is a function of (1) the concentration and localization of non-clay materials (quartz, mica, gibbsite, pyrite, lignite; Fe2O3, TiO2, MnO), (2) the montmorillonite content, (3) the particle size and X-ray crystallinity of the kaolinite, and (4) the texture of the clay aggregate. These mineralogical, chemical and textural variables are not homogeneously distributed but reveal and help to explain differences between samples, layers, pits and the important hard and soft clay types of the region.