LAUSR

Abstract The present study aims to propose a new relationship on the thickness of fundamental kaolinite particles determined by XRD crystallite size (D001) as controlled by its structural order-disorder degree and the kaolin chemical variability (KCV). The average crystallite size (D001) values of 29 kaolinite-rich samples, belonging to two different geologic ages and depositional conditions, show similar positive correlations with the KCV multiplied by the structural order-disorder degree determined by Hinckley (HI) and Lietard (R2) indices (R2 = 0.863 and 0.853), respectively. This relationship is given by the empirical equations: D001 = 99.35 (HI × KCV) + 28.42 and D001 = 141.50 (R2 × KCV) + 24.65. The obtained values are proposed as a new chemo-structural index, named “Azhar-IACT Index”.