Abstract
Clay mineralogy of Vietnam soils was examined. Surface soils were collected from agricultural land at the sites different in parent rocks in four out of seven agroeconomic zones. The soils derived from alluvium and sandstone were light clay, clay loam or sandy clay loam in texture, and the clay fraction was composed of mica and kaolinite with or without chlorite. In addition, the mica/vermiculite/smectite mixedlayer mineral was found in the soils collected from the Red River Delta region, while vermiculite-chlorite intergrade was detected in the soils collected in the North Midland and Mountainous region. The soils derived from limestone were of heavyclay texture, and the clay fraction consisted predominantly of kaolinite. The soils derived from basalt were of heavyclay texture, and the clay mineralogical composition was different with relief. The clay fraction of Ferralsols on the hillside was composed of kaolinite, whereas that of Luvisols on the terrace comprised smectite and halloysite (7Å).
