Newly designed stability diagrams, which consider Al as a mobile, reactive component x(including hydrated Al3+, AI(OH)2+, Al2(OH)4+2, AI(OH)+2 and AI(OH)4species) as well as parameters, Na, K+, H+, and H4SiO4, show that in average river water halloysite and kaolinite are stable with respect to K-feldspar, albite, and nepheline. By contrast, in present sea water, kaolinite alone is stable in a system containing kaolins plus K-feldspar or albite, but both halloysite and kaolinite are stable in a system of kaolins and nepheline.

The geologic observations that kaolinites become more abundant than halloysites through geologic time are interpreted from solution chemistry, Gibbs free energy, and activation energy. Halloysite may crystallize from a solution supersaturated with respect to halloysite, but kaolinite may crystallize under these same conditions or also from a solution saturated with respect to kaolinite. Moreover, any halloysite formed will tend to be spontaneously transformed to kaolinite (ΔGr° being negative). Rate of transformation, however, is governed by the activation energy (not Gibbs free energy), the temperature, and the rate of kaolinite precipitation from such nutrient solutions as may be supplied from dissolution of halloysite through diagenetic processes. Geologic occurrences of kaolinite and halloysite in modern and ancient weathered products are consistent with these theoretical interpretations.

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