An anomalous phillipsite from Saint-Jean-le-Centenaire, Ardèche

Phillipsite occurs as clear transparent spheroids, colourless to yellow to reddish-orange in colour, in the vugs of a basalt at Saint-Jean-le-Centenaire, Ardèche, France. The fibrous radial nature of the spheroids can be observed under the microscope only between crossed polars. It is Si-richer than normal hydrothermal (i.e. occurring in vugs of massive rocks) phillipsites. The powder pattern lacks all those peaks which make the distinction between phillipsite and merlinoite possible. The peak broadening in the powder pattern indicates a crystallite size around 350 Å. On the whole, this anomalous zeolite is more similar to phillipsite than to merlinoite and, in detail, its features are near those of some sedimentary and some synthetic phillipsites.