抄録
Six bentonite beds, called bed A-F, are mined in northern and western Black Hills district, Wyoming. Chemical composition and mineralogical properties of smectites from these bentonite beds have been studied by X-ray powder diffraction method, chemical analysis, differential thermal analysis and infrared spectroscopy. Sodium is dominant interlayer cation in the specimens from bentonite beds, C, D, E and F, though calcium is main exchange cation in the specimen from bentonite bed A. The structural formulae calculated from chemical composition show that smectites from the bed D and E are beidellite, and the others are montmorillonite. The temperature of dehydroxylation peak in DTA curves of all specimens are higher than that of Cheto montmorillonite. The strength of 840cm-1 absorption band in infrared spectra increases with the substitution of Mg for Al in the octahedral sheet. Greene-Kelly test and variation of basal spacings of Na-saturated specimens at various relative humidity indicate that these smectites except bed D are the mixture of phases containing various layer charge component.
