Crystallization damage by sodium sulfate

Experiments demonstrate that a stone containing thenardite suffers great damage when exposed to water below the temperature limit of mirabilite stability. This is due to a transition between thenardite and mirabilite, and not to thenardite reprecipitation. Damage occurs whether or not thenardite was produced previously by mirabilite decomposition. Together with recent results from the literature, these results indicate that damage occurs because thenardite dissolution can produce solutions highly supersaturated with respect to mirabilite, so that precipitation of this mineral can lead to large crystallization pressures. Finally, it appears that there is a salt content threshold beyond which damage increases substantially.