Thermal behaviour of analcimes from two different genetic environments

Hydrothermal analcite (type-H) and leucite-derived analcite (type- X) from different Italian localities have very similar XRD patterns but give different DTA and TG curves. Dehydration of the H-type gives a DTA peak at 350-370 degrees C, whereas the X-type yields a wide band between 235 and 320 degrees C. Activation energy in the H-type analcite is 6.9-7.1 kcal/mole, whilst in the X-type it is 5.3 kcal/mole. Such results are of relative value only, because they are derived from non-isothermal runs and are strongly affected by the method of calculation. Both DTA and TG methods provide evidence for a difference in the H (sub 2) O bonding energies within the analcite structure crystallized in different genetic environments.