Review of existing Mossbauer data

Other workers concerned themselves with characterizing tetrahedral Fe (e.g. Rancourt et al. 1994b). Hogarth et al. (1970) were the first to report Fe in two phlogopite samples from Quebec with parameters of 5 = 0.19 and 0.21 mm/s and A = 

Several studies looked at the thermal oxidation and dehydroxylation of biotite, including Rice and Williams (1969), Bagin et al. (1980), Vicente-Hemandez et al. 

40 mm/s and A = 1.34 mm/s. They suggested that the successive loss of H during oxidation distorts the Fe octahedra and leads to an increase in its A, similar to the idea proposed by Ivanitskiy (1975a). Additional experiments by Chandra and Lokanathan 

A formalized analysis of the EFG was also employed by Bagin et al. (1980) their model effectively explained the large quadrupole splitting that is associated with octahedral Fe, again using vacancies as part of their model. More recently, an elegant paper by Aldridge et al. (1986) used molecular orbital methods to model the electronic structure of biotite. They showed that iterative extended Htickel theory calculations of 

Clarification of Fe-bearing mica terminology was one of the goals of Dyar and Bums (1986). Their data on the mica at Cape Ann, Massachusetts, type locality for annite, showed it to be an oxy-biotite with significant Fe contents (Fig. 5-A). The mica in the Pikes Peak granite of Colorado was shown to be the closest composition to the Fe end-member, annite (Fig. 5-B), as proposed by Winchell (1925). 

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