抄録
Initial analytical testworks employing x-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) performed on the forty (40) clay samples obtained from the Quaternary alluvial type clay resource in Liloan, Cebu, Philippines revealed a seemingly peculiar geographic, stratigraphic and compositional homogeneity of the clay deposit. Mineral assemblages of fine oriented specimens exemplified by XRD patterns showed the dominancy of mixed layer kaolinite-smectite in the clay component and the ubiquity of quartz and feldspar in the non-clay fraction. A complexity in the XRD results arose in the consistent display of large basal reflections averaging 16.3A^°against the usual 15-15.5 A^°theoretical norm accepted for ordinary smectite. Present interpretation postulates this disparity as caused by the integrally random order stacking of layers of kaolinite-smectite assemblage rather than by the existence of appreciable amount and variety of exchangeable cations in the interlayers of smectite mineral alone. Calculated values derived from simulation illustrate the ratio of kaolinite to smectite to be higher at surface horizon but gradually becomes of equal proportion with depth. This is due probably to the degree of differential weathering. Treatment of fine oriented samples with ethylene glycol (EG) disclosed significant expansion of basal distance at an average of 18.5A^°which essentially lends support to the explanation that the samples are mixed-layer mineral of kaolinite-smectite. Samples subjected to 1 hr heat treatment at lower temperature ranges reflected rehydration capability in few hours.
