On the origin of the name kaolin and the kaolin deposits of the Kauling and Dazhou areas, Kiangsi, China

The purpose of this study is to seek information about the origin of the name kaolin and related kaolinite. Also an attempt was made to reveal the true mineral composition of the kaolin and its origin in the type area. A trip was made to both the type locality and adjacent abandoned mining sites. The kaolinized muscovite-granitoid from the Dazhou mining area was studied by methods including optical microscopy, XRD, TEM, SEM, EDS and isotopic analysis. The results revealed that the alteration of the granitic rocks was accomplished in two stages. First, by sericitic alteration of feldspar, probably induced by hydrothermal fluids, and secondly, weathering was superimposed. As verified by SEM examination, the kaolinization was initiated by the formation of composite kaolinite stacks on the edges of sericitic mica sheets through topotactic transformation. However, the occurrence of elongate kaolin particles or halloysite indicates that they are crystallized from aqueous solution subsequent to the formation of kaolinite. It was found that kaolinite stacks that formed from the transformation of sericite always contains a small amount of K-ion, whereas the associated halloysite does not. The kaolin clays obtained from the mining areas near Chingtehchien are generally made up of coarse vermiform kaolinite, fine elongate halloysite, and minor amounts of fine sericitic particles or illite.