The Guoshan kaolin deposit, located in the area from Tongan county town to xinxu of Fujian Province, is of weathering residual type formed by weathering of adamellite.Completely-weathering zone, semi-weathering zone and parent rock can be separated in downward succession, along the weathering profile .The completely-weathering zone (i. e. the main ore body) can be further divided into four mineral segments by estimation of the relative content of kaolinite and halloysite using transmission electron micros- copy .Studies. indicate that kaolin minerals are mainly concentrated in the completely-weathering zone. The clay minerals have been studied systematically by such means as analytical el.,ctron microscopy (AEM)，x-ray diffraction (XRD)，infrared absorption spectra (IR)，chemical analysis and optical examination. The results obtained show that they consist mainly of kaolin minerals (kaolinite and halloysite) associated with small amounts of allophane, imogolite., sodic montmorillonite, hydromuscovita and gibbsite .Kaolinite and halloysite, are common members of the kaoli. group in. the 1:1 dioctah}edral phyllosilica- tes. Allophane can also be regarded as a mineral related to this group. Detailed investigations show that kaoliztite has low degree of order and irregular crystal form in the semi-weathering zone, higher degree of order and pseudo-hexagonal sheet form in the completely-weathering surface soil zone .Such a regular variation in the degree of order and crystal form of kaolinite in the weathering profile of monzonitic granite serves as an indi- cator of the developmental stage of the weathering crust. Halloysite is mainly of 2H20 (7A) type, with transitional types of 10A to 7A and 7A to kaolinite also discovered by XRD and. AEM .The crystals of halloysite are basically spherical and tubular in form. Halloysite contains interlayer water which is readily dehydrated, and dehydration might result in partial or complete splitting amd unrolling of tubes and the formation of the polygo- nal cross section. Having been dried, spherical halloysite takes somewhat polyhedral form due to shrinkage .Morphological feature is very important in the study of kaolin minerals and has been used as a diagnostic criterion to distinguish different mineral species in kaolin minerals.