After 15000 s, bassanite gradually starts its reconversion to gypsum (Fig. ; Fig. , stage IV and V). This transformation is accompanied by a reduction in the surface-to-volume ratio in both the meridian and equatorial directions, leading to a decrease in the B parameter. This is because the crystals of both calcium sulfates change shape during the phase transition. Additionally, the re-precipitation of gypsum from bassanite after 15000 s is characterised by overall lower B values compared to the initial gypsum formed before 4000 s.