Chapter 5. Identification and Characterization of Clays Using Specific X-Ray Diffraction and Computer Modeling

Summary

Identification and characterization of clay minerals is often done using X-ray diffraction (XRD) techniques coupled with computer modeling of diffraction phenomena. The best way to accomplish phase identification is by using an XRD mount that maximizes the orientation of the clay platelets in such a way that the basal (001) reflections are enhanced. Much of the vital information about the crystallographic structures of day minerals can be determined by careful examination of the XRD patterns from these so-called “preferred orientation” mounts, although it should be noted that mounts of randomly oriented crystallites also have their uses. Once a tentative identification has been made from an experimental pattern, computer models that calculate the XRD pattern of clays can be used to confirm or refine the characterization. These computer models con be adjusted to account for instrumental and/or mineralogical parameters that affect the diffraction data, so that a near-perfect fit between the experimental and the modeled XRD pattern can be obtained and the investigator can be reasonably certain of his/her characterization.