Abstract

We obtained oriented Fe-XANES spectra on three amphibole bundles of fiber (i.e., asbestiform morphology), two single-crystal fragments (i.e., nonasbestiform morphology), and one aggregate of thousands of smaller particles (termed herein a “puffball”) by use of a spindle stage mounted on beamline X26A, National Synchrotron Light Source, Brookhaven National Lab. These particles of differing morphology were obtained from a single rock sample collected at the former vermiculite mine near Libby, Montana, U.S.A. The XANES spectra vary as a function of orientation for the singlecrystal fragments and bundles of fibers and were the same regardless of orientation for the puffball. Differences in the spectra for the single-crystal fragments and bundles of fibers indicate variations in Fe oxidation states between the two differing morphologies. Comparison to a calibration line based on amphibole standards allowed determination of Fe 3+ /ΣFe values of 0.69 for the bundles of fibers and 0.60 for the single-crystal fragments, while the puffball had a Fe 3+ /ΣFe value of 0.66. These values agree well with our earlier Mossbauer data on a bulk sample of this same material, with Fe 3+

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