Halloysite is a common pedogenic clay mineral, often found in young soils developed on volcanic deposits (Dixon, 1989). It is a member of the kaolin group of clays with the same ideal stoichiometric composition as kaolinite [A12Si2Os(OH)4 ]. Halloysite, however, often contains water of hydrat ion (i.e., A12Si2Os(OH)4.nH20), and is commonly found with a tubular morphology. This "rol l ing" of ha...

-Selected Brazilian Oxisols were sampled and submitted to high-gradient magnetic separation (HGMS) to study the iron oxide-clay mineral associations. The soils, derived from four different parent materials, have mineralogy dominated mostly by hematite, goethite, and kaolinite. Gibbsite appears in most soil samples. The high-gradient magnetic separation showed good separation for some soils, as ...

[1] Al-rich phyllosilicates (kaolinite, montmorillonite) have been found in layers overlying Fe/Mg-smectites on Mars, and it has been suggested that this stratigraphy formed through in situ leaching at the surface, similar to terrestrial weathering profiles. We are investigating the remotely sensed signatures of this type of weathering using ten samples from a vertical section of altered Deccan...

Direct current resistance measurements were made of kaolinite and serpentine powders to follow the changes in resistances during their dehydroxylation processes in air. The resistance of kaolinite remained almost constant during the dehydroxylation, whereas that of serpentine showed a rapid decrease. The formation of distorted lattice sites where the charge carriers are scattered under an elect...

This computational study performed using the density functional theory shows that hydrated and non-hydrated tetrahedral and octahedral kaolinite mineral surfaces in the presence of a cation adsorb the nucleic acid bases thymine and uracil well. Differences in the structure and chemistry of specific clay mineral surfaces led to a variety of DNA bases adsorption mechanisms. The energetically most...

Introduction Conclusions References