The mechanism for the dehydroxylation of Keokuk kaolinite, dickite, and nacrite (Al 2 Si 2 O 5 (OH) 4 ) was investigated in detail with the aid of powder X‐ray diffraction, the Rietveld method, and infrared spectroscopy. It was determined that these polymorphic clay minerals dehydroxylate via an inhomogeneous mechanism in the range room temperature to 455°C. This result implies that when these samples dehydroxylate (up to 40% dehydroxylated at 455°C) the individual crystallites spontaneously react either completely, to form the metaphase of these minerals, or not at all, retaining all the structural details of the unheated crystalline material. These results amplify previous nuclear magnetic resonance results concerning this mechanism and are used to explain the appearance of the differential thermal analysis curves for these minerals.
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P. R. Suitch (1986) studied this question.
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