Abstract: Soil samples from near Long Xuyen, South Vietnam, considered to be typical of the clayey alluvial soils of the Mekong Delta, were investigated to determine the soil mineral content and soil type. The soils are of fairly uniform composition, consisting mainly of clay minerals and quartz. the predominant clay minerals including illite and chlorite with lesser amounts of kaolinite and smectite. The small hydrous iron oxide content, indicated by fluorescence background intensity, verified that the soils are not latosols but are clayey estuarine soils amenable to future development as arable land.
The method of specimen preparation enabled direct quantitative analysis of the soil samples by X-ray diffraction with the aid of the results of mechanical analysis and of previous analyses of comparable soil samples from the Delta and nearby areas. A method for the quantitative determination of quartz was used that is independent of the powder crystallite orientation. A study of surface replicas of the soil samples by electron microscopy was made to illustrate the fabric of the soil. The undisturbed soil fabric consists mostly of somewhat randomly-oriented large domains of clay minerals with some blocky quartz particles. Nanno-fossils were present in all samples.