gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1960.032.249.03 The Kinetics of the Ordering Process in Triclinic NaAlSi3O8 McConnell J. D. C. M.Sc., M.A., Ph.D. Mckie Duncan M. A.,B.Sc., A.R.I.C., F.G.S. Dept. of Mineralogy and Petrology, Downing Place, Cambridge 6 1960 32 249 436 454 Copyright © 1960, The Mineralogical Society 1960 Summary

A kinetic analysis is presented of the data of MacKenzie (1957) on the hydrothermal treatment of NaAlSi3O8 under isobaric, isothermal conditions in the temperature range 450° C. to 1000° C.

The analysis indicates the existence of a smeared polymorphic transformation in the temperature range around 600° C. The activation energy for the transformation is about 60 kcal. mole−1 and has been equated with the process of self-diffusion involved in Al-Si ordering in the structure. Some dry-heating experiments and the influence of varying water vapour pressure are discussed.