2024 Volume 28 Issue 3-4 Pages 55-66
Four smectite clays in CSSJ reference samples were examined using TEM/STEM imaging and energy-dispersive X-ray spectroscopy (EDS) in SEM and STEM in order to characterize their chemical compositions, grain sizes, impurity minerals, and other properties. Fine calcite particles were commonly found along with quartz in the Tsukinuno samples (JCSS-3101, 3101b), which served as the primary source of calcium, as reported in previous bulk analyses. Cristobalite, quartz, and feldspar are the prevalent impurity minerals in the Mikawa sample (JCSS-3102), and STEM-EDS analysis revealed that the composition of the smectite clay is definitely montmorillonite, with subtle differences from Tsukinuno montmorillonite. The synthetic saponite (JCSS-3501) displayed a wide range of crystal sizes. Sulfate and sodium ions were concentrated in the aggregates of very fine saponite crystallites when compared to particles with larger sizes.
