Green glauconite-like minerals from Weipa, Australia, which were previously known as glauconite, were determined to be unusual Fe-rich vermicuhte and Fe-rich smectite. This study revealed the structural and chemical nature of these unique phyllosilicates with HRTEM, AEM, SEM and XRD analysis.

The Fe-rich phyllosilicates comprising up to about 15 wt% of the rock occur with various amounts of quartz, mica, feldspar, low-Fe smectite, kaolinite, pyrite and siderite at about 30 meters depth in unweathered marine sediments of the Rolling Downs Formation at Weipa. The proportions of Fe-rich vermiculite and smectite decrease upward and become undetectable in the upper saprolite zone at about 23 m depth.

Two major morphologies of the Fe-rich phyllosilicates were observed. One is of tabular or granular detrital-shaped form (Fig.la); the other is platy or film-like, coating grains and occurring in matrix and fissures (Fig.lb).