Glauconite cations

Manghnani, M.H. and Hower, J., 1964. Glauconites cation exchange capacities and infrared spectra. Am. Mineralogist, 49 586-598. 

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 phenomenon of increased hardness occurs principally in minerals of sheet and chain structures, which link together through the cations (silicates and aluminosilicates, as well as hydrated sheet minerals, such as glauconite, melilite and gypsum—M ranging from 0 to about 1.25), and also in minerals of skeletal structures (borates, phosphates, sulphates, nitrates, carbonates, such as calcite, dolomite and others—Ah from 0 to about 1.15). For this reason, the hardness analysis of minerals with weak bonds demands consideration of the fact that just as the basic crystallo-chemical factors, so is hardness influenced by the form of domains (component parts of structures) in all anisodesmic minerals of chain, sheet or skeletal structure. Depending on the form of domain (and also according... 

Fig.5. Histograms showing the distribution of the cations of eighty-two glauconite structhral formulas.

The cation population of the octahedral sheet of glauconite includes a wider range of values than is found for most other 2 1 clays, with possible exception of the beidellites and nontronites. The average for the 82 samples is 2.054 and 77% of the values are larger than 2.00. The values range from 1.94 to 2.31. Some of these high... 

Fig.6. Variations of average interlayer cation total with average octahedral total for sixty-six analyzed glauconites and celadonites. Data divided into eight approximately equal groups. (After Tyler and Bailey, 1961.)...

Ca appears to be slightly more abundant than Na in the exchange positions (Tables XV and XVI) although Foster (1969) found Na to be more common for some glauconites. Analyses reported by Owens and Minard (1960) show that Mg can also be a major exchange cation (Table XX). 

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.)...

Exchange capacity and exchangeable cations of glauconite concentrates from N.J. Sewell (After Owens and Minard, 1960)... 

Analysis No. 1 represents the only truly tetrasilic celadonite. The average value for Si in the 17 analyses is 3.83. Except for Nos. 17-19 variations are between 3.73 and 4.00. Octahedral occupancy is close to 2 for all celadonites, with an average of 2.05. Interlayer cations often number substantially less than 1.0 and average 0.81 with a low value of 0.38 (No. 14). This, of course, is typical also for glauconites and hydrous micas. ... 

When an octahedral sheet has appreciably more Fe3+ (i.e., glauconite) than is present in celadonite, less Mg is needed to provide the total number of large cations (Fe3++Mg). This results in an increase in the total trivalent ions in the octahedral positions. In glauconites the Al + Fe3+ total is larger than 1.3, dominating the octahedral sheet, and a plot indicates there is no relation between the Mg content and the Al/(A1+Fe3+) ratio. 

Present data indicate that Fe3+-rich low-charge clays increase their layer charge by increasing the Mg and Fe2+ content of the octahedral sheet at the expense of Fe3 + more so than of Al. The average Al content of glauconite and celadonite is similar to that of nontronite, but the Fe3+ values are lower. With increased octahedral charge there is an increase anion-anion repulsion and the octahedral sheet increases relatively more in the c direction than the 6 direction, which also favors the large cations. Thus, relatively less tetrahedral Al is required to afford the sheet size differential to allow sufficient tetrahedral rotation to lock the K into place. 

Chapelle, F. H and L. L. Knobel. 1983. Aqueous geochemistry and exchangeable cation composition of glauconite in the Aquia Aquifer. Maryland. Ground Water 21(3) 343-52. 

Bailey SW (1975) Cation ordering and psendosymmetiy in layer sihcates. Am Mineral 60 175-187 Bailey SW (1984a) Classification and structures of the micas. Rev Mineral 13 1-12 Bailey SW (1984b) Crystal chemistry of the true micas. Rev Mineral 13 13-60 Bailey SW (1984c) Review of cation ordering in micas. Clays Clay Minerals 32 81-92 Bailey SW (1986) Report of the AlPEA Nomenclature Committee (llhte, Glauconite and Volkonskoite). AIPEA Newsl 22 1-3... 

Daynyak LG, Drits VA, Heffits LM (1992) Computer simulation of cation distribution in dioctahedral 2 1 layer silicates using IR-data application to Mossbauer spectroscopy of a glauconite sample. Clays Clay Minerals 40 470-479... 

Drits VA, Dainyak LG, Muller F, Besson G, Manceau A (1997) Isomorphous cation distribution in celadonites, glauconites, and Fe-illites determined by Infrared, Mossbauer, and EXAFS spectroscopies. Clay Minerals 32 153-179... 

Doyle CS, Traina SJ, Ruppert H, Kandelewicz T, Rehr JJ, Brown GE Jr (1999) XANES studies at the A1 X-edge of aluminum-rich surface phases in the soil environment. J Synchrotron Rad 6 621-623 Drager G, Frahm R, Materlik G, Briimmer O (1988) On the multiplet character of the X-ray transitions in the pre-edge stmcture of Fe K absorption spectra. Phys Status Solidi 146 287-294 Drits VA, Dainyak LG, Muller F, Besson G, Manceau A (1997) Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mdssbauer and EXAFS spectroscopies. Clay Minerals 32 153-179... 

Hydromicas are authigenic minerals rather easily forming in a sedimentary environment. Fe-illites would be the analogs of glauconites in gradually salting-up basins. The out-flow of bottom waters and the fixation of the bivalent cations Ca and Mg " (in dolomite) in case of a relatively low concentration of the latter (sodic-calcic lakes) lead to the relative enrichment of these in potassium. The latter will then be fixed by the silicate compounds in solution leading to the synthesis of Fe-illites. In case... 

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