Eight scapolite samples from different geologic settings; marialite-meionite series. TG and DTA were used to define the release of the volatile components during heating. In the temperature range up to 800 degrees C, the emission of H 2 O, SO 2 , CO 2 , NaCl, and KCl was observed to occur continuously, but with five evident steps. The presence of SO 2 in the gaseous phase may be due to decomposition reactions. X-ray powder diffractograms indicated an increase in a and V, with a trend inversely proportional to the percentage of meionite present in each sample. Increases in lattice parameters, with rising temperature, and percentage of meionite may be expressed by the equations: da/dT = -1.59 X 10 (sub -6) ME% + 1.85 X 10 (sub -4) (r 2 = 0.996);dV/dT = -0.3 X 10 (sub -3) Me% + 0.034 (r 2 = 0.998).--Modified journal abstract.