Sulphation of both Shoshone fly-ash and its amorphous form may occur up to about 10% wt of SO3. Above that composition, sulphates are separated from silicates and may create necks between silicate particles. There is evidence that sulphated ash may consist of species with sodalite structures such as hauyne, with maximum sulphur content between 5 and 8% wt. These may stabilise the sulphated silicate-sulphate interface below 1000 degrees C.