Sodalite shows positive thermal expansion (PTE) up to 800 K, then expansion stops and it start to contract between 900 and 1000 K, in apparent agreement with observations which found the inversion of the expansion behaviour at about 700 K . It must be noted that while experimental measurements found a PTE for sodalite minerals in this wide range of T, 26 the study of Leardini et al found for pure silica sodalite PTE betwen 273 and 573 K and NTE above 653 K. These differences were ascribed to the neutral nature of the organic template they used in the synthesis, which once calcinated did not interfere with the framework, allowing the contraction of the structure.