Characterization of kaolin/smectite mixed layer mineral in paleudult of Java Island

Abstract

In a Paleudult of Java Island, there was a clay mineral indicating a mixed layer mineral which gave 15.51 A peak (in the range of 14.63 A and 16.37 A) on Mg 2+ -air dry and a 20.55 A peak on Mg 2+ -glycerol solvation. On K - -saturation, the mineral showed an 11.87 A peak and this peak was continuous to 7.53 A. Furthermore, on sequential heating, the peak gradually shifted and finally shifted completely to 10.05 A at 550°C in X-ray diffraction (XRD). A peak of 7.53A was also observed in both Mg 2+ - and K + -saturated clays which disappeared after heating at 550°C. The objective of this study was to investigate the characteristics of this mineral. The 060 peak was 1.50 A and suggests the dioctahedral smectite. The Greene-Kelly test on the clay sample suggests beidellite. Formamide solvation that caused a swelling of the 7.53 A peak to 10.05 A suggests the presence of halloysite. The 5M NaOH treatment resulted in a collapse of the 7.53A peak and remained at a sharp peak of 15.50 A (in Mg 2+ -saturated clay). The presence of halloysite was also supported by a SiO 2 /Al 2 O 3 molar ratio of NaOH extractable materials. The NaOH treatment also resulted in an increase of the 11.87 A peak (in K + -saturated clay) to 13.49 A. According to the mineralogical and chemical properties of the clay sample we consider that the mineral is halloysite/beidellite mixed layer mineral.