Enantiomorphism of kaolinite: Manifestation at the levels of elementary layer and microcrystals

The right and left forms of the argillaceous mineral kaolinite (Al2 Si2O5(OH)4), which is wide-spread in nature, have been revealed for the first time by transmission electron microscopy and gold decoration in vacuum. The enantiomorphic forms of this mineral are established at the level of the elementary 7 Å layer, which determines the kaolinite structure, and at the level of nano- and microcrystals typical of this mineral. Both kaolinite forms are widespread in ancient and young weathering crusts. Enantiomorphic kaolinite microcrystals are formed in two ways: through the periodic formation of 2D nuclei and via helical growth, which is dominant for both kaolinite forms. The right- and left-handed kaolinite forms are observed in the samples under study with equal probability.