No regional zoning of zeolite assemblages was apparent in this study Figure 8 shows that the zoning sequence and textural evidence suggest the following crystallisation sequence: first K-rich clay (nontronite) followed by K-rich mica (celadonite), carbonate (calcite), cryptocrystalline silica (e g chalcedony), then thomsonite followed by chabazite, analcime, phillipsite and wairakite, and natrolite, laumontite, and stilbite-type minerals (stilbite and stellerite) Zeolites' stability ields are known from modern hydrothermal systems (Kristmannsdottir and Tomasson, 1978) and the observed sequence in the samples studied here conformed to a progressive decrease in temperature favouring hydrothermal system hydration.
Thomsonite is the most common zeolite phase formed after nontronite/celadonite Chabazite, analcime, phillipsite and probably wairakite are the irst zeolites which became crystallised.
The main phases identified in the alkaline reaction of FEBEX bentonite are phillipsite, Mg-clays, analcime, tobermorite and CSH-gels.
Phillipsite precipitates rather than analcime when sodium activities decrease.
1990, Epitactic inter-growth of the zeolites phillipsite and gismondite from Gr.
1993, Replacement and incrustation pseudomorphs of zeolites gismon-dite, chabazite, phillipsite and natrolite, N.
Robie, Thermodynamic Properties of Zeolites; Low- Temperature Heat Capacities and Thermodynamic Functions for Phillipsite
and Clinoptilolite; Estimates of the Thermochemical Properties of Zeolitic Water at Low Temperature, Am.
Using the FJPZ50 sample as starting material, a progressive loss of its amorphous character turned it into a synthesis product characterised by the appearance of relative poorly crystalline phillipsite only after 96 hours.
As shown in Figure 7, there was an almost complete transformation of the starting materials into high purity faujasite-type zeolite and phillipsite, although relictic phases (quartz and albite) of the starting materials still remained in the synthesis products.
An undetermined member of the phillipsite
series has been found as very small (less than 0.
The best, with sharp, lustrous crystals up to 3 mm, were collected at the beginning of the 1990's in braunite veins, associated with carbonates, barite and, in places, phillipsite
Sure enough, the major species on the specimen was phillipsite
, but there was also present a number of groups of blocky, rectangular, colorless crystals in groups which appeared to be highly twinned.