Baur W H , Joswig W , Neues Jahrbuch fur Mineralogie, Monatshefte , 1996 (1996) p.171-187, The phases of natrolite occurring during dehydration and rehydration studied, by single crystal X-ray diffraction methods between room temperature and 923 K, Locality: Khibiny, Kola peninsula, Russia, Sample: T = 823 K, crystal III, high natrolite