Solid glauconite

Other resolubilized trace metals precipitate as replacement ions in existing solids such as fecal pellets and bone. Examples of these fiassilized materials include barite, phosphorite, and glauconite. These precipitates contain small amounts of a variety of trace metals as well as other elements. As a result, their chemical composition is variable and their structure is usually amorphous, making it difficult to assign them an empirical formifia. 

Table 5.53 lists the general classification of micas with their main compositional terms. Stoichiometry obeys the general formula XF2 3Z40io(OH,F)2, where X = interlayer cations, Y = octahedrally coordinated cations of the 2 1 mixed layer, and Z = tetrahedrally coordinated cations of the 2 1 mixed layer. It must be noted that several compositional terms are indeed solid mixtures of more elementary components. In particular, glauconite has a complex chemistry and an Al Si diadochy of 0.33 3.67. (R and R terms in table 5.53 identify generic divalent and trivalent cations, respectively.)... 

The most important observation which can be made after the analysis of the chemical and phase equilibria information is that illite and glauconite mineral series, do not overlap. Solid solution is not continuous, neither in the mica-like phase alone nor in mixed layering between mica and expanding layers. Glauconite is not a subspecies of illite. 

Adding SO 4 will give [SO4""] as a new independent variable, which does not seem to be fixed by any new phase. On the other hand, when a small amount of BaO is added, we get BaS04 as a new phase. When we add FeO and Fe2Oa, two new solid phases may be formed, tentatively FeOOH and glauconite. One might continue in this way, adding new phases or new concentration variables. 

Fig.8. The relation between cation exchange capacity and percent expandable layers in glauconites. Solid dots represent one sample open circles two samples dashed line represents trend excluding points with > 30% expanded layers solid line represents C.E.C. (mequiv./lOO g) = 8.2 + 0.54 (% expanded layers). (After Manghnani and Hower, 1964.)...

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