Mineral geochemical analyses (core rim traverses of plagioclase and pyroxene) of samples recovered during IODP Expedition 398 (Site U1595). Site U1595 (proposed Site CSK-08B) is located in the southern basin of the Santorini caldera at 291 meters below sea level (mbsl). It was drilled in three holes (U1595A–U1595C) to a maximum recovery depth of 127.0 meters below seafloor. The data files also contain BSE images of plagioclase and pyroxene crystals that illustrate where the geochemical traverses were done. Mineral geochemical analyses and BSE images were generated by electron probe micro-analysis, using facilities at the Natural History Museum London. Data analysis was supported by NERC - UK IODP Phase 4 Moratorium Award, NERC Grant NE/X016374/1, Ralf Gertisser. For sample context, see: https://publications.iodp.org/proceedings/398/398title.html https://doi.org/10.14379/iodp.proc.398.109.2024