Kaolin minerals in the Amazon soils [Brazil]

The kaolin minerals in the Amazon upland soils vary ranging from the well-crystallized triclinic/b-axis disordered kaolinite intermediate in a red yellow latosol and a red yellow podzolic soil to the disordered kaolinite/halloysite (7 Å) intermediate in a "Terra Roxa Estruturada" soil and a reddish brunizem. The particle size of kaolin minerals become smaller, and their structural randomness increase, with the increase of iron content of the clay fractions in the Amazon upland soils.