The aim of this paper is to describe a technique for recording the intensity distribution along definite crystallographic directions by using a classical 0,20 powder goniometer. This method was developed for application to highly oriented powders. In the calculation of simulated spectra, the partial misorientation of the particles is considered. The reflection intensities and profiles are compared for different shapes of the misorientation function N(~).

Secondary micas after smectite, including mix illite–smectite phases, can form in sediments by three mechanisms, each being specific to particular environments. As the process develops, the newly formed phases undergo structure ordering. Two mechanisms involve transformation of 2:1 mixed-layer structures, and the third is the growth of screw dislocations, with formation of ordered mix phases having a Reichweite parameter of R = 1 or R = 2. We propose methods for identifying such phases when they are present in small amounts or when their XRD patterns lack well-pronounced superperiodic reflections, as well as mathematical formalism for illitization modeling. The theoretical issues are illustrated with field examples, and the illitization mechanisms are discussed in terms of their possible practical applications.

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