This paper gives a thorough characterization of the structural evolution of clay minerals that are present in the Rotliegende sandstone reservoir, lower Slochteren, of the Broad Fourteens Basin, the Netherlands (Southern North Sea), resulting from contrasting burial histories which have affected several blocks. The early kaolinite crystallization is followed by a steady kaolinite-dickite diagenetic transformation affecting both the structure and the morphology of kaolin-group minerals. Kaolinite ＇＇books＇＇ are first replaced by dickite pseudomorphs which are subsequently replaced by dickite blocky crystals with increasing burial depth. Intermediate structures between both end-members are difficult to characterize with X-ray diffraction. However, both differential thermal analysis (DTA) and infrared spec spectroscopy allow an accurate and fast characterization of this kaolinite-dickite evolution. The structural characteristics of kaolin-group minerals are related to the burial history experienced by the sediments prior to the Cimmerian orogeny. During the Cimmerian orogeny, kaolin-group minerals are suddenly illitized. With the increase of temperature conditions prevailing during this hydrothermal-like event, I the morphology of illitic minerals steadily evolves from hairy illite to lath-shaped particles and ultimately to isometric plates. The size of illitic crystals also increases with increasing temperature conditions. At the same time, structural characteristics of illitic minerals also evolve; this evolution is followed by the decomposition oi experimental X-ray diffraction profiles. The decomposition method allows us to determine simultaneously the illite over I-S ratio, the illite content in I-S, and illite crystallinity. The evolution of the three-dimensional structure oi illitic minerals, from 1M with trans vacant sites towards 1M with cia vacant sites with increasing temperature, is determined by X-ray diffraction on randomly oriented preparations. The morphological and structural characteristics of illitic minerals do not represent the progress of a smectite-illite transformation but these characteristics clearly reflect the temperature conditions prevailing during the illitization of kaolin (similar to 155 My). Morphological and structural characteristics of both kaolin-group and illitic minerals may be characterized efficiently with X-ray diffraction, DTA, and infrared spectroscopy. Once the diagenetic sequence oi clay mineral neoformation has been determined, these characteristics can be used to constrain estimations oi palaeoburial depths.