Generally, an increase in anisotropy is correlated with larger crystal sizes and aspect ratios. Conversely, at T > 80 °C (> 4800 s), the decrease in anisotropy indicates a dissolution-reprecipitation process, since it correlates with a decrease in the crystal size of gypsum and concurrent nucleation and subsequent growth of isotropic nano-sized bassanite crystals. This effect becomes evident through analysis of the changes in the ⍴ parameter, calculated from the pseudo-invariant expressing q 2 -weighted integral intensity: