The Ferric Analogue of Pyrophyllite and Related Phases

Ferripyrophyllite and related Fe3+-rich 2:1 clays in Recent deposits of Atlantis II Deep, Red Sea

“…The reflections 13,20, 15,24,31 and 06,33 close to 2.59, 1.71 and 1.51 A respectively, are clearly observed. The 06,33 spacing at 1-51 A is consistent with ferric dioctahedral 2:1 clays (Weaver & Pollard, 1973;Wise & Eugster, 1964;Chukhrov et al, 1979a;Eggleton, 1977). A broad diffraction effect, near 3.20 A, is probably a 00l reflection.…”

“…The non-expanding layers gave d(001) spacings <10 ~ and in the range 9.6-9.8 ~ on air dried and glycolated preparations. It must be noted that clay particles analysed by XRD contain only few associated layers (see also TEM results), with the result that the maxima of the 001 reflections are shifted toward lower angles (Brindley & Brown, 1980); the true d (001) (Wise & Eugster, 1964) and are closer to those given by Chukhrov et al (1979a) for ferripyrophyllite (9.57-9.72 A).…”

Cation Distribution, Mössbauer Spectra, and Magnetic Properties of Ferripyrophyllite

“…Charge defects that might possibly be responsible for the second doublet are a trivalent tetrahedral cation neighbor, a divalent octahedral cation neighbor, or defects in the shell of anion neighbors. From the formula reported by Chukhrov et al (1979a), and quoted in the introduction, the probability of a trivalent ion appearing ina tetrahedral site is 0.20/4 = 0.05. Each octahedral site has four tetrahedral sites as neighbors, so the random probability of having at least one trivalent tetrahedral neighbor is given by the binomial distribution as…”

“…It is quite possible, however, that the sites responsible for the second doublet are not distributed at random, but are located in the hydroferripyrophyllite (smectite) phase whose swelling layers are intercalated by Ca (Chukhrov et al, 1979a). The third doublet can be attributed to iron on tetrahedral sites, on the basis of its isomer shift (see Annesten et al, 1971).…”

“…The third doublet can be attributed to iron on tetrahedral sites, on the basis of its isomer shift (see Annesten et al, 1971). It follows that aluminum has no overriding preference for tetrahedral sites unoccupied by silicon; 80% of them are actually occupied by Fe 3 § Thus, the formula of Chukhrov et al (1979a) should be modified to read:…”