Denis Rancourt
J.M. Daniels, H.-Y. Lam, D.G. Rancourt, J.A. Westgate, D. York
Earth and Planetary Science Letters
Volume 73, Issues 2–4, May 1985, Pages 430-438
https://doi.org/10.1016/0012-821X(85)90090-1
Abstract
Magnetite (Fe3O4) has the spinel structure, which has two cation sites which also contain vacancies. The spinel structure is also stable over large deviations from stoichiometry. Fe3O4 has a phase transition at 120 K, and physical properties at room temperature can be very different from those at liquid nitrogen temperature. It is magnetic at room temperature and is thus easily separated magnetically from any mineral of which it is a component. For these reasons, it seems an ideal substance for fingerprinting minerals by Mössbauer spectroscopy, since it is capable of exhibiting large variations in its physical properties.
The room temperature Mössbauer spectra of seven samples of magnetite extracted from volcanic ash were found to be sufficiently different that different sources could be distinguished by visual inspection. A least-squares analysis showed that the spectra could be composed of 3 relaxing six-line patterns. The ratios of the intensities of these patterns, and ratios of their relaxation times, gave 5 parameters which appear to characterize the different sources of the tephra. One of these parameters appears to be a function of the temperature of crystallization of the magnetite.