EARLY REACTION DETERMINATION IN TWO HYDROXIDE-KAOLINITE SYSTEMS BY ELECTRON MICROSCOPY AND DIFFRACTION fry

RESULTS of the study of the kaolinite-sodium hydroxide interaction sliowed extensive dissolution of the kaolinite structure at particle edges, with some production of " silicate relicts " as a secondary effect. The method of specimen preparation for electron micro-scopy precluded electron-diffraction study of soluble reaction products. The study of the kaolinite-calcium hydroxide interaction revealed a similar at tack on particle edges and formation of " silicate relics " and, in addition, formation of an insoluble reaction product tha t was tentatively identified by electron diffraction as prehnite, Ca2Al2Si30i|,(OH)2. Both studies showed an ephemeral phase that, by selected area elec-tron diffraction, appeared to be a layer lattice silicate in (001) orientation. In the calcium hydroxide-treated kaolinite, formation of the reaction product was followed from nucleation along particle edges, after 24 hr, to growth of particles about 0.5 to 1 / « in size after 15 days. The combination of electron microscopy of surface replicas to detect changes in morphology with selected area electron diffraction of parallel pseudoreplicas for identification shows promise as a tool for study of the early stages in mineral-chemical interaction