Glauconite occurrence

Eh and pH at which the process takes place. In both cases the role of organic material is evident and similar, acting as a motor in changing the aspect of the silicate in the pellet both in chemistry and mineralogy from that of the enclosing sediment. The reasons for the development of one mineral species or the other are at the moment somewhat obscure but, considering the similarity of the occurrence, the mechanism is probably the same. With this in mind the analysis which follows for sedimentary glauconites can be considered applicable for sedimentary 7 X chlorite pellets. 

Chemical conditions. The occurrence of glauconites in sandstones (acid) and carbonates (basic) indicates that pH is not of great importance to their formation. They are found in sedimentary rocks ranging in age from Precambrian to the present day. Hence, their formation seems to be constrained by chemical and physical conditions rather than by specific events. There is no apparent time-dependent reaction which transforms them into new phases. 

Some glauconites have been identified in hydrothermally altered basalts together with celadonites (Alt et al., 1992 Clayton and Pearce, 2000). This material appears to form a mixed-layer mica-ferric smectite series. The formation of glauconite mixed-layer minerals is therefore not restricted to peloids under shallow-ocean-bottom conditions. However, the identification of glauconite as distinct from ferric Ulite is difficult. Perhaps these mineral occurrences should be given another name. 

Young, H.R. Doig, D.J. (1986) Petrography and provenance of the Glauconitic Sandstone, south-central Alberta, with comments on the occurrence of detrital dolomite. Bull. Can. Petrol. Geol, 34, 408-425. 

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